初中提公因式3道要详细1.(x+1)(x+2)(x-4)(x-5)+92.x平方(x+1)-y平方(y-1)+xy3.2a平方b(b+2)

(x+1)(x+2)(x-4)(x-5)+9
=(x+1)(x-4)(x+2)(x-5)+9
=(x²-3x-4)(x²-3x-10)+9
=(x²-3x)²-14(x²-3x)+49
=(x²-3x-7)²
x²(x+1)-y²(y-1)+xy
=x³+x²-y³+y²+xy
=(x-y)(x²+xy+y²)+(x²+xy+y²)
=(x²+xy+y²)(x-y+1)
第三题题目不清