I'm on my math book studying exponential equations, and I got stuck on this Problem:
What is sum of the roots of the equation: $\frac{16^x + 64}{5} = 4^x + 4$
I decided to changed: $4^x$ by $m$, so I got: $\frac{m^2 + 64}{5} = m + 4$
working on it I've got: $m^2 - 5m + 44 = 0$
but solving this equation the roots were: $x = \frac{5 \pm \sqrt{151i}}{2}$ which isn't even close from the possible answers: 1, 3, 8, 16 or 20.
What's the mistake ? thanks in advance;