一、选择题
1.计算(2a-3b)(2a+3b)的正确结果是(B )
A.4a2+9b2 B.4a2-9b2 C.4a2+12ab+9b2 D.4a2-12ab+9b2
2.若(x+a)(x+b)=x2-kx+ab,则k的值为( B )
A.a+b B.-a-b C.a-b D.b-a
3.计算(2x-3y)(4x2+6xy+9y2)的正确结果是(C )
A.(2x-3y)2 B.(2x+3y)2 C.8x3-27y3 D.8x3+27y3
4.计算(a2+2)(a4-2a2+4)+(a2-2)(a4+2a2+4)的正确结果是( D )
A.2(a2+2) B.2(a2-2) C.2a3 D.2a6
5.方程(x+4)(x-5)=x2-20的解是(A )
A.x=0 B.x=-4 C.x=5 D.x=40
6.若2x2+5x+1=a(x+1)2+b(x+1)+c,那么a,b,c应为( C )
A.a=2,b=-2,c=-1 B.a=2,b=2,c=-1
C.a=2,b=1,c=-2 D.a=2,b=-1,c=2
7.若6x2-19x+15=(ax+b)(cx+b),则ac+bd等于( D )
A.36 B.15 C.19 D.21
8.(x+1)(x-1)与(x4+x2+1)的积是( C )
A.x6+1 B.x6+2x3+1 C.x6-1 D.x6-2x3+1
二、填空题
1.(3x-1)(4x+5)=12X²+11X-5
2.(-4x-y)(-5x+2y)=20X²-3XY-2Y²
3.(x+3)(x+4)-(x-1)(x-2)=10X+10
4.(y-1)(y-2)(y-3)=Y³-6Y²+11Y-6
5.若(x+a)(x+2)=x2-5x+b,则a=-7,b=-14
1、计算下列各式
(1)(2x+3y)(3x-2y)
=6x²-4xy+9xy-6y²
=6x²+5xy-6y²
(2)(x+2)(x+3)-(x+6)(x-1)
=x²+2x+3x+6-(x²-x+6x-6)
=x²+5x+6-x²-5x+6
=12
(3)(3x2+2x+1)(2x2+3x-1)
=6x^4+9x³-3x²+4x³+6x²-2x+2x²+3x-1
=6x^4+13x³+x²+x-1
(4)(3x+2y)(2x+3y)-(x-3y)(3x+4y)
=6x²+9xy+4xy+6y²-(3x²+4xy-9xy-12y²)
=6x²+13xy+6y²-3x²+5xy+12y²
=3x²+18xy+18y²