检验下列因式分解是否正确1:xy-1=(x-1)(y+1)2:a²-2ab-8b²=(a-4b)(a+2b)

Question

检验下列因式分解是否正确
1:xy-1=(x-1)(y+1)
2:a²-2ab-8b²=(a-4b)(a+2b)

Answer 1

(x-1)(y+1)=x(y+1)-(y+1)=xy+x-y-1不等于xy-1 错
(a-4b)(a+2b)=a(a+2b)-4b(a+2b)=a²+2ab-4ab-8b²=a²-2ab-8b² 对