5^x - 5^(3-x) = 20
solving for x. not sure how to go about this
I'll kick this off for you,
$\displaystyle 5^x - 5^{3-x} = 20$
$\displaystyle 5^x - \frac{5^3}{5^x} = 20$
Now mulitply both sides through by $\displaystyle 5^x$ we get
$\displaystyle 5^{2x} - 5^3 = 20\times 5^x$
Making $\displaystyle a = 5^x$ then
$\displaystyle a^2 - 5^3 = 20a$
Can you solve this quadratic?