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a)\(\frac{3y}{4x}+\frac{5y}{4x}=\frac{3y+5y}{4x}=\frac{8y}{4x}=\frac{2y}{x}\)

b)\(\frac{x^2+1}{2x-4}-\frac{7x}{2-x}=\frac{x^2+1}{2\left(x-2\right)}-\frac{-7x}{x-2}\)

\(=\frac{x^2+1}{2\left(x-2\right)}-\frac{-7x\times2}{\left(x-2\right)\times2}=\frac{x^2+1+14x}{2\left(x-2\right)}\)

18 tháng 12 2021

a: \(=\dfrac{4x-2+6x^2-6x+2x^2+1}{2x\left(2x-1\right)}=\dfrac{8x^2-2x-1}{2x\left(2x-1\right)}\)

 

20 tháng 6 2021

a/ 5x2y (x2y– 4xy2 + 7xy)

`=5x^4y^2-20x^3y^3+35x^3y^2`

b/ 3xy2 (x2y3 + x 2y – xy2 )

`=3x^3y^5+3x^3y^3-3x^2y^4`

c/ 3x(12x2 + 4x – 5) + 2x(9x2 – 6x + 7)

`=36x^3+12x^2-15x+18x^3-18x^2+14x`

`=54x^3-6x^2-x`

d/ 5x(2x2 – 9x – 5) – 9x (x2 - 7x – 4)

`=10x^3-45x^2-25x-9x^3+63x^2+36x`

`=x^3+18x^2+11x`

13 tháng 11 2017

https://www.youtube.com/watch?v=cFZDEMTQQCs

24 tháng 12 2020

a, \(\frac{x+1}{2x+6}+\frac{2x+3}{x^2+3x}=\frac{x+1}{2\left(x+3\right)}+\frac{3x+2}{x\left(x+3\right)}\)

\(=\frac{x^2+x}{2x\left(x+3\right)}+\frac{6x+4}{2x\left(x+3\right)}=\frac{x^2+7x+4}{2x\left(x+3\right)}\)

b, Sua de :  \(\frac{3}{2x+6}-\frac{x-6}{2x^2+6x}=\frac{3}{2\left(x+3\right)}-\frac{x-6}{2x\left(x+3\right)}\)

\(=\frac{3x}{2x\left(x+3\right)}-\frac{x-6}{2x\left(x+3\right)}=\frac{2x+6}{2x\left(x+3\right)}=\frac{1}{x}\)

20 tháng 12 2021

c: \(=\dfrac{x^3+2x+2x^2+2x+x^2-x+1}{\left(x+1\right)\left(x^2-x+1\right)}\)

\(=\dfrac{x^3+3x^2+3x+1}{\left(x+1\right)\left(x^2-x+1\right)}=\dfrac{x^2+2x+1}{x^2-x+1}\)

21 tháng 12 2020

\(\frac{x^2+2}{2xy^3}-\frac{2x+2}{2xy^3}=\frac{x^2+2-2x-2}{2xy^3}=\frac{x^2-2x}{2xy^3}=\frac{x\left(x-2\right)}{2xy^3}=\frac{x-2}{2y^3}\)

\(\frac{4}{x-5}-\frac{1}{x+5}+\frac{13x-x^2}{25-x^2}=\frac{4}{x-5}-\frac{1}{x+5}+\frac{x^2-13x}{x^2-25}\)

\(=\frac{4\left(x+5\right)}{\left(x-5\right)\left(x+5\right)}-\frac{x-5}{\left(x-5\right)\left(x+5\right)}+\frac{x^2-13x}{\left(x-5\right)\left(x+5\right)}\)

\(=\frac{4x+20-x+5+x^2-13x}{\left(x-5\right)\left(x+5\right)}\)

\(=\frac{x^2-10x+25}{\left(x-5\right)\left(x+5\right)}=\frac{\left(x-5\right)^2}{\left(x-5\right)\left(x+5\right)}=\frac{x-5}{x+5}\)

14 tháng 12 2020

\(\frac{x+2}{x}+\frac{2x-1}{2-x}-\frac{x-8}{x^2-2x}\)

\(=\frac{x+2}{x}-\frac{2x-1}{x-2}-\frac{x-8}{x\left(x-2\right)}\)

\(=\frac{\left(x-2\right)^2}{x\left(x-2\right)}-\frac{x\left(2x-1\right)}{x\left(x-2\right)}-\frac{x-8}{x\left(x-2\right)}\)

\(=\frac{x^2-4x+4-2x^2+x-x+8}{x\left(x-2\right)}=\frac{-x^2-4x+12}{x\left(x-2\right)}\)

\(=\frac{\left(x+6\right)\left(x-2\right)}{x\left(x-2\right)}=\frac{x+6}{x}\)