①a(a+4)-24
=a²+4a-24
没法算,看题目是否有错?
②Y^3+y^2-20y
=y(y²+y-20)
=y(y+5)(y-4)
③X^2-(2x-3)^2
=(x+2x-3)(x-2x+3)
=(3x-3)(-x+3)
=-3(x-1)(x-3)
④(x+y）²-（x+Y）-2
=(x+y-2)(x+y+1)
⑤（a-b）^2+6(b-a)+5
=(a-b)²-6(a-b)+5
=(a-b-5)(a-b-1)
⑥x^2-2xy-8y^2
=(x-4y)(x+2y)
⑦(a^2+5a+3)(a^2+5a-2)-6
=(a²+5a)²+(a²+5a)-12
=(a²+5a+4)(a²+5a-3）
=(a+1)(a+4)(a²+5a-3)