5^(x+2)-5^(x-1) = 25分之124
问题描述：
5^(x+2)-5^(x-1) = 25分之124
答
5^(x+2)-5^(x-1) =124/25
25*5^x-5^x/5=124/25
(25-1/5)*5^x=124/25
(124/5)*5^x=124/25
5^x=1/5=5^(-1)
x=-1