1.下列计算正确的是( )
A.2a2·2a2=4a2 B.2x2·2x3=2x5 C.x·y=(xy)4 D.(-3x)2=9x2
2.若 ,则等于( ) A.8 B.15 C.45 D.75
3.(-x2y3)3·(-x2y2)的结果是( ) A.-x7y13 B.x3y3 C.-x8y13 D.-x7y5
4.(x+4y)(x-5y)的结果是( )
A.x2-9xy-20y2 B.x2+xy-20y2 C.x2-xy-20y2 D.x2-20y2
5.如果(ax-b)(x+2)=x2-4,那么( )
A.a=1,b=-2 B.a=-1,b=-2; C.a=1,b=2 D.a=-1,b=2
