Precalc
posted by Amy on .
How to solve for x:
2^(2x) + 2^(x) 12 = 0
Steps too
I tried solving this but I ended with ln(12) / 2ln(2) + ln(2) but the real answer is supposed to be ln(3) / ln(2) or 1.585

let 2^x= y
then your equation becomes
y^2 + y  12 = 0
(y+4)(y3) = 0
so y = 4 or y = 3
then
2^x= 4, which is not possible
or
2^x = 3
ln both sides
ln(2x) = ln3
x ln2 = ln 3
x = ln3/ln2 = appr. 1.58