# Rewriting equation

• Dec 2nd 2009, 10:45 AM
BabyMilo
Rewriting equation
$2^x+28*(2^{-x})=11
$

show how this can be rewritten as

$(2^x)^2-11*2^x+28=0$

thanks
• Dec 2nd 2009, 10:56 AM
earboth
Quote:

Originally Posted by BabyMilo
$2^x+28*(2^{-x})=11
$

show how this can be rewritten as

$(2^x)^2-11*2^x+28=0$

thanks

$2^x+28*(2^{-x})=11~\implies~2^x+\dfrac{28}{2^x}-11=0
$

Now multiply both sides of the equation by $2^x$ and you'll get the given result at once.