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=_________.
计算:(1)10m×10 000=_________; (2)3n-4×(-3)3×35-n=__________.
已知am=3,an=4,化简下列各式:(1)am+1=______; (2)a3+n=_______; (3)am+n+2=_______.