Cái này cũng gọi là chứng minh???

Điều hiển nhiên mà

Chứng minh sao được taaa :P Mời cao nhân :D

Lấy zí dụ mà CM

hihi 

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ĐKXĐ:\(x\ne\pm2;x\ne-3;x\ne0\)

\(P=1+\frac{x-3}{x^2+5x+6}\left(\frac{8x^2}{4x^3-8x^2}-\frac{3x}{3x^2-12}-\frac{1}{x+2}\right)\)

\(=1+\frac{x-3}{\left(x+2\right)\left(x+3\right)}\left[\frac{8x^2}{4x^2\left(x-2\right)}-\frac{3x}{3\left(x^2-4\right)}-\frac{1}{x+2}\right]\)

\(=1+\frac{x-3}{\left(x+2\right)\left(x+3\right)}\left(\frac{2}{x-2}-\frac{x}{x^2-4}-\frac{1}{x+2}\right)\)

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

\(=1+\frac{x-3}{\left(x+2\right)\left(x+3\right)}\cdot\frac{2x+4-x-x+4}{\left(x-2\right)\left(x+2\right)}\)

\(=1+\frac{8\left(x-3\right)}{\left(x+2\right)^2\left(x+3\right)\left(x-2\right)}\)

Đề sai à ??

\(ĐK:x\ne\pm1\)

\(\Leftrightarrow\frac{ax^2-x+ax-1+bx-b}{x^2-1}=\frac{a\left(x^2+1\right)}{x^2-1}\)

\(\Leftrightarrow\frac{ax^2+x\left(a-1+b\right)-b-1}{x^2-1}=\frac{ax^2+a}{x^2-1}\)

\(\Leftrightarrow\hept{\begin{cases}x\ne\pm1\\a+b-1=0\\-b-1=a\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}x\ne\pm1\\a+b-1=0\\-b-1=a\end{cases}}\)

Giải ra :D

đề bài là gì??!!!!

tính ớ bạn

A = \(\frac{1}{x}\left(\frac{x^2-xy}{x+y}\right)^2\left[\frac{x+y}{\left(x-y\right)^2}+\frac{x+y}{xy-y^2}\right]-\frac{x}{x+y}\)

A = \(\frac{1}{x}\left(\frac{x^2-xy}{x+y}\right)^2\left[\frac{x+y}{\left(x-y\right)^2}+\frac{x+y}{y\left(x-y\right)}\right]-\frac{x}{x+y}\)

A = \(\frac{1}{x}\left[\frac{x\left(x-y\right)}{x+y}\right]^2\left[\frac{y\left(x+y\right)+\left(x-y\right)\left(x+y\right)}{y\left(x-y\right)^2}\right]-\frac{x}{x+y}\)

A = \(\frac{1}{x}\cdot\frac{x^2\left(x-y\right)^2}{\left(x+y\right)^2}\left[\frac{xy+y^2+x^2-y^2}{y\left(x-y\right)^2}\right]-\frac{x}{x+y}\)

A = \(\frac{x\left(x-y\right)^2}{\left(x+y\right)^2}\cdot\frac{x\left(x+y\right)}{y\left(x-y\right)^2}-\frac{x}{x+y}\)

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

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

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                                                   Bài giải

\(\left(x-3\right)2-\left(x-3\right)\left(x+3\right)=0\)

\(\left(x-3\right)\left(x+3-2\right)=0\)

\(\left(x-3\right)\left(x+1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-3=0\\x+1=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=-1\end{cases}}\)

\(\Rightarrow\text{ }x\in\left\{3\text{ ; }-1\right\}\)

\(\left(x-3\right).2-\left(x-3\right)\left(x+3\right)=0\Leftrightarrow\left(x-3\right)\left[2-\left(x+3\right)\right]=0\)

\(\Leftrightarrow\left(x-3\right)\left(2-x-3\right)=0\Leftrightarrow\left(x-3\right)\left[\left(-1\right)-x\right]\). Xét 2 trường hợp

Xét 2 trường hợp. \(TH1:x-3=0\Leftrightarrow x=0+3=3\)

\(TH2:\left(-1\right)-x=0\Leftrightarrow x=\left(-1\right)-0=-1\). Vậy \(x\in\left\{-1;3\right\}\)

\(\frac{4}{x^2-3x+2}-\frac{3}{2x^2-6x+1}+1=0\)

<=> \(\frac{4}{\left(x-1\right)\left(x-2\right)}-\frac{3}{2x^2-6x+1}+1=0\)

<=> 4(2x² - 6x + 1) - 3(x - 1)(x - 2) + (x - 1)(x - 2)(2x² - 6x + 1) = 0

<=> 28x² - 30x + 2x⁴ - 12x³ = 0

<=> 2x(14x - 15 + x² - 6x²) = 0

<=> 2x(x² - 3x + 5)(x - 3) = 0

vì x² - 3x + 5 khác 0 nên:

<=> 2x = 0 hoặc x - 3 = 0

<=> x = 0 hoặc x = 3

\(\frac{4}{x^2-3x+2}-\frac{3}{2x^2-6x+1}+1=0\)

\(\Leftrightarrow\frac{2x^4-12x^3+28x^2-30x}{2x^4-12x^3+28x^2-15x+2}=0\)

\(\Leftrightarrow2x^4-12x^3+28x^2-30x=0\)

\(\Leftrightarrow2\left(x-3\right)\left(x^2-3x+5\right)=0\)

mà  \(x^2-3x+5\) khác 0 

\(\Rightarrow\orbr{\begin{cases}2x=0\\x-3=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x=3\end{cases}}\)