Question

4^(x+2) + 6*4^(x-1) =70

Answer 1

 4^(x+2) + 6*4^(x-1) =70

16·(4^x)+(6/4)·(4^x)=70
(4^x)(16+3/2)=70
(4^x)(32+3)/2=70
4^x=(70·2)/35
4^x=4  x=1

проверка
4^(1+2) + 6*4^(1-1) =4³+6·1=64+6=70 верно