Posted by **logarithms** on Monday, January 14, 2008 at 1:07pm.

how do you perform this??

log x + log(x+3) = 1

- algebra -
**Reiny**, Monday, January 14, 2008 at 1:13pm
One of the main rules of logs is

Log(AB) = Log A + Log B, as long as the base is the same

so log x + log(x+3) = 1

Log (x(x+3)) = 1

Log(x^2 + 3x) = 1

x^2 + 3x = 10^1

x^2 + 3x - 10 = 0

(x+5)(x-2) = 0

x=-5 or x=2

but in log x , x must be greater than 0

so x = 2

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