# How do you solve 7^(2-10r)+1=46?

Aug 20, 2016

4.376x${10}^{-} 3$

#### Explanation:

${7}^{2 - 10 r}$ +1=46
So ${7}^{2 - 10 r}$ =45

Remember ${2}^{3}$ =8 is the same thing ${\log}_{2}$8 =3

So I can write the equation as :

${\log}_{7}$45 =2-10r
Rearranging gives us 10r=2-${\log}_{7}$45

10r =0.04376..
r=4.376x ${10}^{-} 3$