$\\1,$

MTC : $36x^2y^2$

Quy đồng :

$\dfrac{1}{9xy^2}=\dfrac{4x}{36x^2y^2}\\\dfrac{-5}{12x^2}=\dfrac{-15y^2}{36x^2y^2}$

$2,$

MTC : $(x-3)(x+3)$

Quy đồng :

$\dfrac{x^2}{x+3}=\dfrac{x^2(x-3)}{(x-3)(x+3)}=\dfrac{x^3-3x^2}{(x-3)(x+3)}\\\dfrac{5}{x-3}=\dfrac{5(x+3)}{(x-3)(x+3)}=\dfrac{5x+15}{(x-3)(x+3)}$

$3,$

MTC : $(x-1)(x+1)$

Quy đồng :

$\dfrac{3-x}{x+1}=\dfrac{(3-x)(x-1)}{(x-1)(x+1)}=\dfrac{-x^2 + 4x-3}{(x-1)(x+1)}\\\dfrac{x}{x^2-1}=\dfrac{x}{(x-1)(x+1)}$

$4,$

MTC : $5x(x-2)$

Quy đồng :

$\dfrac{1-x}{5x-10}=\dfrac{1-x}{5(x-2)}=\dfrac{x-x^2}{5x(x-2)}\\\dfrac{1+x}{x^2-2x}=\dfrac{1+x}{x(x-2)}=\dfrac{5+5x}{5x(x-2)}$
$5,$

MTC : $x(x-1)(x+1)$

Quy đồng :

$\dfrac{4x-1}{x^2-x}=\dfrac{4x-1}{x(x-1)}=\dfrac{4x^2+3x-1}{x(x-1)(x+1)}\\\dfrac{4x}{1-x^2}=\dfrac{-4x}{(x-1)(x+1)}=\dfrac{-4x^2}{x(x-1)(x+1)}$

Đáp án:

 

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