Question

(x+2)(x+3)+x^2-5x-8 x^3-x^2y-xy^2+y^3 18x^2-21xy+5y^2因式分解（写出

Answer 1

(x+2)(x+3)+x^2-5x-8

=x^2+5x+6+x^2-5x-8

=2x^2-2

=2(x^2-1)

=2(x+1)(x-1);

x^3-x^2y-xy^2+y^3

=(x^3-x^2y)-(xy^2-y^3)

=x^2*(x-y)-y^2*(x-y)

=(x-y)(x^2-y^2)

=(x-y)(x-y)(x+y)

=(x+y)(x-y)^2;

18x^2-21xy+5y^2

=(3x-y)(6x-5y).