Question

因式分解！急！！！！！！！有加分

1.(x+2y)(x+2y-4)+4
2.9（x+1）²（x-1）²-6（x²-1）y+y²
3.（a+2b-3c）²-（a-2b+3c）²

Answer 1

1.(x+2y)(x+2y-4)+4
=(x+2y)²-4(x+2y)+4
=(x+2y-2)²

2.9（x+1）²（x-1）²-6（x²-1）y+y²
=9（x²-1）²-6（x²-1）y+y²
=[3(x²-1)+y]²

3.（a+2b-3c）²-（a-2b+3c）²
=[(a+2b-3c）+（a-2b+3c）][a+2b-3c）-（a-2b+3c）]
=2a(4b-6c)
=4a(2b-3c)