Problem: If 102y=2510^{2 y}=25102y=25, then 10−y10^{-y}10−y equals:
Answer Choices:
A. −15-\dfrac{1}{5}−51
B. 1625\dfrac{1}{625}6251
C. 150\dfrac{1}{50}501
D. 125\dfrac{1}{25}251
E. 15\dfrac{1}{5}51 Solution:
102y=52,10y=5,10−y=1/10y=1/510^{2 y}=5^{2}, 10^{y}=5,10^{-y}=1 / 10^{y}=1 / 5102y=52,10y=5,10−y=1/10y=1/5.