Giải các hệ phương trình sau bằng phương pháp cộng đại số:
a) \(\left\{{}\begin{matrix}3x+y=3\\2x-y=7\end{matrix}\right.;\)
b) \(\left\{{}\begin{matrix}2x+5y=8\\2x-3y=0\end{matrix}\right.;\)
c) \(\left\{{}\begin{matrix}4x+3y=6\\2x+y=4\end{matrix}\right.;\)
d) \(\left\{{}\begin{matrix}2x+3y=-2\\3x-2y=-3\end{matrix}\right.;\)
e) \(\left\{{}\begin{matrix}0,3x+0,5y=3\\1,5x-2y=1,5\end{matrix}\right..\)
b)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%202x%20+%205y%20%3D8%20%26%20%26%20%5C%5C%208y%20%3D%208%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%202x%20+%205y%20%3D8%20%26%20%26%20%5C%5C%20y%20%3D%201%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D%5Cfrac%7B3%7D%7B2%7D%20%26%20%26%20%5C%5C%20y%20%3D%201%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
c)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%204x%20+%203y%20%3D6%20%26%20%26%20%5C%5C%20y%20%3D%20-2%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D3%20%26%20%26%20%5C%5C%20y%20%3D%20-2%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
d)![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%202x%20+%203y%20%3D-2%20%26%20%26%20%5C%5C%203x%20-2y%20%3D%20-3%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%206x%20-%209y%20%3D%20-6%20%26%20%26%20%5C%5C%206x%20-%204y%20%3D%20-6%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%206x%20-%209y%20%3D%20-6%20%26%20%26%20%5C%5C%20-5y%20%3D%200%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D%20-1%20%26%20%26%20%5C%5C%20y%20%3D%200%20%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
e)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%201%2C5x%20+%202%2C5y%3D15%20%26%20%26%20%5C%5C%201%2C5x%20-%202y%20%3D%201%2C5%20%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%201%2C5x%20%3D7%2C5%26%20%26%20%5C%5C%20y%20%3D%203%20%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
Bài giải:
a)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%205x%20%3D10%20%26%20%26%20%5C%5C%202x%20-y%20%3D%207%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D2%20%26%20%26%20%5C%5C%20y%20%3D%202x-7%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D2%20%26%20%26%20%5C%5C%20y%20%3D%20-3%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
b)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%202x%20+%205y%20%3D8%20%26%20%26%20%5C%5C%208y%20%3D%208%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%202x%20+%205y%20%3D8%20%26%20%26%20%5C%5C%20y%20%3D%201%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D%5Cfrac%7B3%7D%7B2%7D%20%26%20%26%20%5C%5C%20y%20%3D%201%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
c)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%204x%20+%203y%20%3D6%20%26%20%26%20%5C%5C%20y%20%3D%20-2%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D3%20%26%20%26%20%5C%5C%20y%20%3D%20-2%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
d)![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%202x%20+%203y%20%3D-2%20%26%20%26%20%5C%5C%203x%20-2y%20%3D%20-3%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%206x%20-%209y%20%3D%20-6%20%26%20%26%20%5C%5C%206x%20-%204y%20%3D%20-6%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%206x%20-%209y%20%3D%20-6%20%26%20%26%20%5C%5C%20-5y%20%3D%200%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%20x%20%3D%20-1%20%26%20%26%20%5C%5C%20y%20%3D%200%20%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
e)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%201%2C5x%20+%202%2C5y%3D15%20%26%20%26%20%5C%5C%201%2C5x%20-%202y%20%3D%201%2C5%20%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5CLeftrightarrow)
![This is the rendered form of the equation. You can not edit this directly. Right click will give you the option to save the image, and in most browsers you can drag the image onto your desktop or another program.](http://latex.codecogs.com/gif.latex?%5Cleft%5C%7B%5Cbegin%7Bmatrix%7D%201%2C5x%20%3D7%2C5%26%20%26%20%5C%5C%20y%20%3D%203%20%26%20%26%20%5Cend%7Bmatrix%7D%5Cright.)