计算:(1)105×1 000+40 0000×103;
(2)x3·xm-xm+3;
(3)(2x-1)2·(2x-1)3+(2x-1)4·[-(2x-1)].
已知a+b+c=2,求22a-3·24b+3·22a+4c的值.
已知5x=7,5y=2,求5x+y+3的值.
计算:
(1)2x3·x2-x2·x3+2x4·x;
(2)yn-1·y2·y+yn-2·y3·y;
(3)(m-n)4·(m-n)·(n-m)3.
计算:(1)(-2)×(-2)2×(-2)3=_____________; (2)(-x)9·x5·(-x)5·(-x)3=___________;(3)an+4·a2n-1·a____________;
若m·23=26,则m=_________.