# Indices Problem!

• March 13th 2011, 01:06 AM
jakethasnake
Indices Problem!
using indices only, and the substitution y=2^x , solve the equation:

2^2x - 6.2^x + 8 = 0
• March 13th 2011, 01:18 AM
Unknown008
Okay, could you perform the substitution?
• March 13th 2011, 01:23 AM
Prove It
Maybe it will help if you rewrite your equation as

$\displaystyle \left(2^x\right)^2 - 6\cdot 2^x + 8 = 0$...
• March 13th 2011, 01:28 AM
jakethasnake
im lost as to where the substitution goes? and the question is written exactly as shown out of previous exam paper.
• March 13th 2011, 03:31 AM
HallsofIvy
Look at Prove It's response. See those " $2^x$"s? Replace those with y.
• March 13th 2011, 03:34 AM
Prove It
Quote:

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 $\displaystyle x$.