十字相乘法,1.9(a-b)²12(a²-b²)+4(a+b)²因式分解的结果A.（5a-b)² B.（5a+b)² C.(3a-2b)(3a+2b) D.(5a-2b)²2.(x-y)²-3(x-y)-40第一题打错了，应是9(a-b)²+12(a²-b²)+4(a+b)²还有

十字相乘法,1.9(a-b)²12(a²-b²)+4(a+b)²因式分解的结果A.（5a-b)² B.（5a+b)² C.(3a-2b)(3a+2b) D.(5a-2b)²2.(x-y)²-3(x-y)-40第一题打错了，应是9(a-b)²+12(a²-b²)+4(a+b)²还有
十字相乘法,
1.9(a-b)²12(a²-b²)+4(a+b)²因式分解的结果
A.（5a-b)² B.（5a+b)² C.(3a-2b)(3a+2b) D.(5a-2b)²
2.(x-y)²-3(x-y)-40
第一题打错了，应是9(a-b)²+12(a²-b²)+4(a+b)²
还有3题
1.（2x+y)²+(2x+y)-2
2.x²+11xy+18y²
3.6x²-17x-10=( )(3x-10)

十字相乘法,1.9(a-b)²12(a²-b²)+4(a+b)²因式分解的结果A.（5a-b)² B.（5a+b)² C.(3a-2b)(3a+2b) D.(5a-2b)²2.(x-y)²-3(x-y)-40第一题打错了，应是9(a-b)²+12(a²-b²)+4(a+b)²还有
1.9(a-b)²+12(a²-b²)+4(a+b)²
=[3(a-b)]²+2[3(a-b)][2(a+b)]+[2(a+b)]²
=[3(a-b)+2(a+b)]²
=(5a-b)²
2.(x-y)²-3(x-y)-40
1 5
1 -8
=[(x-y)+5][(x-y)-8]
=(x-y+5)(x-y-8)
3.(2x+y)²+(2x+y)-2
1 2
1 -1
=(2x+y+2)(2x+y-1)
4.x²+11xy+18y²
1 2
1 9
=(x+2y)(x+9y)
3.6x²-17x-10=(2x+1 )(3x-10)
3 -10
2 1

2.（X-Y-8）(X-Y+5)

1.选A 9(a-b)²+12(a²-b²)+4(a+b)²=9a²-18ab+9b²+12a²-12b²+4a²+8ab+4b²=25a²-10ab+b²=5a-b)²

1、A
2、(x-y-8)(x-y+5)
3、(2x+y+2)(2x+y-1)
4、(x+2y)(x+9y)
5、2x+1