4^x+1=64 (2/3)^x=27/8 4^x+1+4^x=320 ! !

4^(x+1)=64
4^(x+1)=4^3
x+1=3
x=2

(2/3)^x=27/8
(2/3)^x=(3/2)^3
(2/3)^x=(2/3)^(-1)
x=-1

4^(x+1)+4^x=320
4^x*(4+1)=320
4^x=320:5
4^x=64
4^x=4^3
x=3