Question

Find x
10^log(x^2 + 2x) = 15

Answer 1

10^log(x^2+2x) is the same as x^2+2x

therefore, x^2+2x=15

x^2+2x-15=0

use quadratic formula:

x= (-2 + sqrt(4+60))/2 or
x= (-2 - sqrt(4+60))/2

x= (-2 + 8)/2 = 3 or
x=(-2-8)/2= -5

x= 3 or -5

Answer 2

if A=10^B then log(A)=B

therefore
A=10^log(A) that's where I got it :)