Đáp án+Giải thích các bước giải:
a)
3x-3y-$x^2$+2xy-$y^2$
=(3x-3y)-($x^2$-2xy+$y^2$)
=3(x-y)-$(x-y)^2$
=(x-y)(3-x+y)
b)
$x^2$-$4x^2y^2$+$y^2$+2xy
=($x^2$+$y^2$+2xy)-$4x^2y^2$
=$(x+y)^2$-$4x^2y^2$
=(x+y-2xy)(x+y+2xy)
c)
$(x+y)^3$-(x-y)^3$
=($x^3$+3$x^2$y+3x$y^2$+$y^3$)-($x^3$-3$x^2$y+3x$y^2$-$y^3$)
=$x^3$+3$x^2$y+3x$y^2$+$y^3$-$x^3$+3$x^2$y-3x$y^2$+$y^3$
=$6x^2$y+$2y^3$
=2y(3$x^2$+$y^2$)
d)
$x^2$-5x-14
=($x^2$+2x)-(7x+14)
=x(x+2)-7(x+2)
=(x+2)(x-7)
