Indices question?

Question

What are the steps to solve this
3^(2x) - 7(3^(x)) = 18

Please list down clearly all steps taken to derive the answer. Thanks

Answer 1

Let y = 3^x, then your equation becomes:
y^2 - 7y = 18
y^2 -7y -18 = 0
(y - 9)(y + 2) = 0
y = 9 ; y = -2[extraneous]
3^x = 9
3^x = 3^2
x = 2