[Toán 8]tìm A biết

B

baochau15

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K

khaiproqn81

$A+\frac{15}{x^3+1}$=$\frac{5}{x+1}-\frac{10}{x-(x^2-1)}$
$A=-\frac{15}{(x+1)(x^2-x+1)}+\frac{5}{x+1}-\frac{10}{x-(x^2-1)}$
$A=-\frac{15}{(x+1)(x^2-x+1)}+\frac{5}{x+1}+\frac{10}{x^2-x+1)}$
$A=-\frac{15}{(x+1)(x^2-x+1)}+\frac{5x^2-5x+5}{(x+1)(x^2-x+1)}+\frac{10x+10}{x^2-x+1)}$
$A=\frac{-15+5x^2-5x+5+10x+10}{(x+1)(x^2-x+1)}$
$A=\frac{5x^2+5x}{(x+1)(x^2-x+1)}$
$A=\frac{5x(x+1)}{(x+1)(x^2-x+1)}$
$A=\frac{5x}{x^2-x+1}$
Nhớ thank nha
 
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