Question 822396: log base 10 (x+4) + log base 10 (x+1) = 1
Answer by LinnW(1048)   (Show Source):
You can put this solution on YOUR website! log base 10 (x+4) + log base 10 (x+1) = 1
log(x+4) + log(x+1) = 1
Since log(10) = 1
log(x+4) + log(x+1) = log(10)
log((x+4)*(x+1)) = log(10)
(x+4)*(x+1) = 10
x^2 + 5x + 4 = 10
subtract 10 from each side
x^2 + 5x - 6 = 0
(x+6)(x-1) = 0
x = -6 or x = 1
substituting in log(x+4) + log(x+1) = 1 and x = 1
log(1+4) + log(1+1) ?= 1
log(5) + log(2) ?= 1
log(5*2) ?= 1
log(10) ?= 1 Yes this looks good.
So x = 1
A negative value for x will not work.
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