Bài 1:
a) 3x2 - 3y2
= 3(x2 - y2)
= 3(x - y)(x + y)
b) x2 - xy + 7x - 7y
= x(x - y) + 7(x - y)
= (x - y)(x + 7)
c) x2 - 3x + 2
= x2 - x - 2x + 2
= x(x - 1) - 2(x - 1)
= (x - 1)(x - 2)
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1.
a,\(3x^2-3y^2\)
\(=3\left(x^2-y^2\right)\)
\(=3\left(x-y\right)\left(x+y\right)\)
b,\(x^2-xy+7x-7y\)
\(=\left(x^2-xy\right)+\left(7x-7y\right)\)
\(=x\left(x-y\right)+7\left(x-y\right)\)
\(=\left(x+7\right)\left(x-y\right)\)
c,\(x^2-3x+2\)
\(=x^2-2x-x+2\)
\(=\left(x^2-x\right)+\left(-2x+2\right)\)
\(=x\left(x-1\right)-2\left(x-1\right)\)
\(=\left(x-2\right)\left(x-1\right)\)
d,\(x^3+2x^2+xy^2-16x\)
\(=x\left(x^2+2x+y^2-16\right)\)
2.
a,\(\dfrac{2x+6}{3x^2-x}:\dfrac{x^2+3x}{1-3x}\)
\(=\dfrac{2\left(x+3\right)}{x\left(3x-1\right)}:\dfrac{x\left(x+3\right)}{-\left(3x-1\right)}\)
\(=\dfrac{2\left(x+3\right)}{x\left(3x-1\right)}:\dfrac{-x\left(x+3\right)}{3x-1}\)
\(=\dfrac{2\left(x+3\right)}{x\left(3x-1\right)}.\dfrac{3x-1}{-x\left(x+3\right)}\)
\(=\dfrac{2}{-x.x}\)
\(=\dfrac{2}{-\left(x^2\right)}\)
\(=-\dfrac{2}{x^2}\)