# Solving an Exponential Equation

I'm having a hard time with this exponential equation, I'm sure I'm doing some kind of a "minor" mistake again somewhere along the way. Your help is very much appreciated.

$$4\cdot4^{2x}-9\cdot 4^x+2=0$$

*Answers given are: $0,5; -1$.

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Let $y=4^x$. The equation $$4\cdot4^{2x}-9\cdot 4^x+2=0$$ $$4\cdot(4^x)^2-9\cdot 4^x+2=0$$ becomes a quadratic $$4y^2-9y+2=0,$$ which we can solve with the quadratic formula. Then, once you've found the two values for $y$, solve for $x$ using $y=4^x$.