Cách làm cho bạn:
$a) 3x - 6y = 3 . x - 3 . 2y = 3(x - 2y)$
$b) \frac{2}{5}x^{2} + 5x^{3} + x^{2}y = x^{2} (\frac{2}{5} + 5x + y)$
$c) 14x^{2}y – 21xy^{2} + 28x^{2}y^{2} = 7xy . 2x - 7xy . 3y + 7xy . 4xy = 7xy(2x - 3y + 4xy)$
$d) \frac{2}{5}x(y - 1) - \frac{2}{5}y(y - 1) = \frac{2}{5}(y - 1)(x - y)$
$e) 10x(x - y) - 8y(y - x) = 10x(x - y) - 8y[-(x - y)]$
$= 10x(x - y) + 8y(x - y)$
$= 2(x - y)(5x + 4y)$
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