# Math Help - Indices Problem!

1. ## Indices Problem!

using indices only, and the substitution y=2^x , solve the equation:

2^2x - 6.2^x + 8 = 0

2. Okay, could you perform the substitution?

3. Maybe it will help if you rewrite your equation as

$\displaystyle \left(2^x\right)^2 - 6\cdot 2^x + 8 = 0$...

4. im lost as to where the substitution goes? and the question is written exactly as shown out of previous exam paper.

5. Look at Prove It's response. See those " $2^x$"s? Replace those with y.

6. Originally Posted by HallsofIvy
Look at Prove It's response. See those " $2^x$"s? Replace those with y.
And once you have done that, solve for $\displaystyle y$, the solution of which you can use to solve for $\displaystyle x$.