## Solve 2^(2x) - 7(2^x) - 8 = 0 (Hint: Let y = 2^x)

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.
little_dragon
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### Solve 2^(2x) - 7(2^x) - 8 = 0 (Hint: Let y = 2^x)

I know some about powers and about solving by factoring. One of my "challenge" problems is to solve 2^(2x) - 7(2^x) - 8 = 0, and the hint in the book says "Let y = 2^x". I think this gives me y^2 - 7y - 8 = 0. Is that right? Because then I'm pretty sure I can finish this. Thanks.

stapel_eliz
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little_dragon wrote:I think this gives me y^2 - 7y - 8 = 0. Is that right?

That's exactly right!

Now factor, and set each factor equal to zero. Once you've done that, plug the $2^x$ back in for the y, and use what you know about powers to find the answers.

If you get stuck, please reply showing how far you got. Thank you!

Eliz.