计算:(2a-3b)·(-3a)=_______;(-3x2)(-x2+2x-1)=___________;(-2x3y)·(3xy2-3xy+1)=____________.
计算:(-5a4)·(-8ab2)=_________;(-x2y)3·(-3xy2)2=__________;(6×103)×(9×106)=___________.(用科学记数法表示)
化简xy[xy(xy-1)+1]的结果为( )
A. x2y2-xy+1 B. x3y3-x2y2+xy
C. x3y3-xy+1 D. x3y3+xy+1
下列计算不正确的是( )
A. (4×106)×(8×1015)=3.2×1022 B. (-ax)·(-by)=abxy
C. -0.2xy2+x·xy=0 D. (ax2)n·(axn)2=an+2x4n
要使方程x(x2+a)+3x-2b=x3+5x+4成立,则a,b的值分别是( )
A. 2,2 B. -2,-2 C. 2,-2 D. -2,2
下列计算正确的是( )
A. (-4x)(2x2+3x-1)=-8x3-12x2-4x
B. (6xy2-4x2y+1)·3xy=18x2y3-12x3y2
C. (-x)(2x+x2-1)=-x3-2x2+1
D. (-3x2y)·(-2xy+3yz+1)=6x3y2-9x2y2z-3x2y