1)8^(2х+1) =0,125
8^(2х+1)=1\8
8^(2х+1)=8^(-1)
2х+1=-1
2х=-2
х=-1
___________________
2)log5 (x-4)+log. x=1
log5 (x^2-4x)=1
log5 (x^2-4x)=log5 5
x^2-4x=5
x^2-4x-5=0
D=16+20=36
x1=-1;x2=5
____________________
3)2^(x+4) -2^x=120
2^x(2^4 -1)=120
2^x(16-1)=120
2^x=120\15
2^x=8
2^x=2^3
x=3