Đáp án:
$b) 9x^4y^3 +3x^2y^4$
$ = 3x^2y^3(3x^2y + y)$
$c) x^3 -2x^2+5x$
$= x(x^2-2x+5)$
$f) (x^2-25)^2 -(x-5)^2$
$ = (x^2-25 -x+5)(x^2-25 +x-5)$
$ = (x^2-x-20)(x^2+x-30)$
$g) (4x^2-25)^2 -9(2x-25)^2$
$= [4x^2-25 - 3(2x-25)] .[4x^2-25 +3(2x-25)]$
$ =[4x^2 -25 -6x +75] . [ 4x^2 -25 +6x- 75]$
$ = (4x^2 -6x +50) .(4x^2 +6x -100)$