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

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Question 804824: logx+log(x+21)=2
Found 2 solutions by erica65404, Alan3354:
Answer by erica65404(394) About Me  (Show Source):
You can put this solution on YOUR website!
when you add logs together it is the same as multiplying the numbers u are logging.
example:
loga+logb=log(ab)
You need to do this to this problem
log%28x%29%2Blog%28x%2B21%29=2
log%28x%28x%2B21%29%29=2
when log doesn't have a number where the base should be, it means the base is zero.
turn this into an exponential equation.
10%5E2=x%28x%2B21%29
100=x%5E2%2B21x
0=x%5E2%2B21x-100
Now factor the equation.
%28x-25%29%28x%2B4%29=0
x= 25, -4

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
logx+log(x+21)=2
log%28x%2A%28x%2B21%29%29+=+2
x%2A%28x%2B21%29+=+100
x%5E2+%2B+21x+-+100+=+0
(x+25)*(x-4) = 0
x = 4
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You can't use x = -25, log(-25) is not allowed