Question

（1）2a三次方-2a²b+8b-8a （2）3a三次方-3ab²-21a²-21ab （3）-81-8ab+a²+16b²

（4）（a+3）m²+（a+3)m-12a-36 （5）a²（x-y)²-2a（x-y)三次方+（x-y)四次方

（6）（a²+b²-c²）²-4a²b² 都是因式分解

Answer 1

1、=2a²(a-b)-8(a-b)
=2(a-b)(a²-4)
=2(a-b)(a+2)(a-2)
2、=3a(a²-b²)-21a(a+b)
=3a(a+b)(a-b)-21a(a+b)
=3a(a+b)(a-b-7)
3、=a²-8ab+(4b)²-81
=(a-4b)²-9²
=(a-4b+9)(a-4b-9)
4、=（a+3）m²+（a+3)m-12(a+3)
=(a+3)(m²+m-12)
=(a+3)(m+4)(m-3)
5、= （x-y)²[a²-2a(x-y)+(x-y)²]
=(x-y)²[a-(x-y)]²
=(x-y)²(a-x+y)²
6、（a²+b²-c²）²-4a²b²
= （a²+b²-c²）²-(2ab)²
=(a²+b²-c²+2ab)(a²+b²-c²-2ab)
=[(a²+2ab+b²)-c²][(a²-2ab+b²)-c²]
=[(a+b)²-c²][(a-b)²-c²]
=(a+b+c)(a+b-c)(a-b+c)(a-b-c)