How do you do this?
$3^{2x}-5(3^x)+4=0$

Solving:
it’s a quadratic equation! Replace $3^x$ with u.
$u^2 - 5u + 4 = 0$
$(u - 4)(u - 1) = 0$
$u = 4$
$3^x = 4$
$x \log 3 = \log 4$
$x = \ log 4 / \log 3$ or
$u = 1$
$3^x = 1$
$x = 0$