SOLUTION: 25^x + 2 * 5^x = 15

Question 557496: 25^x + 2 * 5^x = 15
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
25^x + 2 * 5^x = 15
25^x=5^2x
..
5^2x+2*5^x-15=0
..
let u=5^x
u^2=5^2x
u^2+2u-15=0
(u+5)(u-3)=0
u=-5
or
u=3
..
For u=-5
5^x≠-5 (reject, 5^x>0)
..
For u=3
5^x=3
take log of both sides
xlog5=log3
x=log3/log5≈0.6826
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