Câu 1
$a,x^4-x$
$=x(x^3-1)$
$=x(x^3-1^3)$
$=x(x-1)(x²+x+1)$
$b, 3(x+3)-x²+9$
$=3(x+3)-(x²-3²)$
$=3(x+3)-(x-3)(x+3)$
$=(3-x+3)(x+3)$
Câu 2
$a,\frac{4}{x-1}+\frac{2}{1-x}+\frac{x}{x-1}$
$=\frac{4}{x-1}-\frac{2}{x-1}+\frac{x}{x-1}$
$=\frac{4-2+x}{x-1}$
$=\frac{2+x}{x-1}$
$b, \frac{2x}{2x-2y}:\frac{x^2}{x-y}$
$=\frac{2x}{2(x-y)}.\frac{x-y}{x^2}$
$=\frac{1}{x}$
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#4/1/2021