典例1
解 (1)$m^{22} ÷ m^2 = m^{22-2} = m^{20}$.
(2)$(-q)^6 ÷ (-q) = (-q)^{6-1} = (-q)^5 = -q^5$.
(3)$(-ab)^7 ÷ (-ab)^3 = (-ab)^{7-3} = (-ab)^4 = a^4b^4$.
(4)$(-z-y)^4 ÷ (z+y)^3 = (z+y)^4 ÷ (z+y)^3 = z+y$.
典例2
解 $\because x^m =5, x^n=25,$
$\therefore x^{5m-2n} = x^{5m} ÷ x^{2n}$
$=(x^m)^5 ÷ (x^n)^2$
$=5^5 ÷ (25)^2$
$=5^5 ÷5^4 =5.$
典例3
答案 C
解析 $(2x-1)^0$有意义,则$2x-1 ≠0$,
解得$x ≠ \frac{1}{2}.$
故选 C.