SOLUTION: log (x+21) + log x = 2

Question 35087: log (x+21) + log x = 2
Found 2 solutions by stanbon, Prithwis:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
log (x+21) + log x = 2
log[x(x+21)]=2
x(x+21)=10^2=100
x^2+21x-100=0
(x+25)(x-4)=0
x=-25 or x=4
x=-25 is extraneous as you see if you put that value into the original problem.
x=4 is a valid solution.
Cheers,
Stan H.

Answer by Prithwis(166) (Show Source): You can put this solution on YOUR website!
log (x+21) + log x = 2
log[x(x+21)]=2
x(x+21)=10^2=100
x^2+21x-100=0
(x+25)(x-4)=0
x=-25 or x=4
x cannot be -25 because log cannot be on negative real numbers;
So, x=4

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