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Giải:
4xn (7xn-1 + x - 5) - 2xn-2 (14xn+1 - 10x2)
= 28x2n-1 +4xn + 1 – 20xn - 28x2n-1 + 20xn
= 4xn+1
![](https://rs.olm.vn/images/avt/0.png?1311)
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a) \(\left(7-14x\right)\left(x-2\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}7-14x=0\\x-2=0\end{cases}\Leftrightarrow\orbr{\begin{cases}14x=7-0\\x=2\end{cases}\Leftrightarrow}}\orbr{\begin{cases}14x=7\\x=2\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{2}\\x=2\end{cases}}}\)
Vậy \(x\in\left\{\frac{1}{2};2\right\}\)
b) \(\left(2x+1\right)\left(x-3\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}2x+1=0\\x-3=0\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=-1\\x=3\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=\frac{-1}{2}\\x=3\end{cases}}}\)
Vậy \(x\in\left\{-\frac{1}{2};3\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Mk ko ghi laj đề nha
\(=\left(17x^4:4x^2\right)-\left(5x^3:4x^2\right)+\left(2x^2:4x^2\right)\)
\(=\frac{17}{4}x^2-\frac{5}{4}x+\frac{2}{4}\)
\(=\frac{17}{4}x^2-\frac{5}{4}x+\frac{1}{2}\)
MK KO GHI LAJ ĐỀ NHA
\(=\left(17x^4:4x^2\right)-\left(5x^3:4x^2\right)+\left(2x^2:4x^2\right)\)
\(=\frac{17}{4}x^2-\frac{5}{4}x+\frac{1}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1) \(\left(x-3\right)^2-4=0\)
\(\Leftrightarrow\left(x-3-2\right)\left(x-3+2\right)=0\)
\(\Leftrightarrow\left(x-5\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=1\end{matrix}\right.\)
2) \(x^2-2x=24\)
\(\Leftrightarrow x^2-2x-24=0\)
\(\Leftrightarrow x^2+4x-6x-24=0\)
\(\Leftrightarrow x\left(x+4\right)-6\left(x+4\right)=0\)
\(\Leftrightarrow\left(x+4\right)\left(x-6\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(3x-1\right)\left(2x-3\right)\left(2x-3\right)\left(x+5\right)=0\)
Th1 : \(3x-1=0=>x=\frac{1}{3}\)
Th2 : \(2x-3=0=>x=\frac{3}{2}\)
TH3 : \(x+5=0=>x=-5\)
Mik tl mà chẳng có ai T kì quá z
2x² - 14x - 120 = 0
<=>2.(x2-7x-60)=0
<=>x2-7x-60=0
<=>x2-12x+5x-60=0
<=>x.(x-12)+5.(x-12)=0
<=>(x-12)(x+5)=0
<=>x-12=0 hoặc x+5=0
<=>x=12 hoặc x=-5