将4^x-2^(x+1)-8=0分解得2^2x-2*2^x-8=0
2^2x-2*2^x+1=9
(2^x-1)^2=9
2^x-1=±3
得2^x=4 2^x=-2(舍去)
x=2
4^x-2^(x+1)-8=0
2^2x-2*2^x-8=0
2^2x-2*2^x+1=9
(2^x-1)^2=9
2^x-1=±3
2^x=-2(舍去)或2^x=4
2^x=4
x=2
4^x-2^(x+1)-8=0
2^2x-2*2^x-8=0
2^2x-2*2^x+1=9
设y=2^x则(y-1)^2=9
(y-1)^2=9
y-1=±3 y=-2或y=4
即2^x=-2(舍去)或2^x=4
2^x=4
x=2