SOLUTION: log10 x + log10 (x+21)=2 1og10[x(x+21)=2 x^2+21x=2 x^2+21x-2=0

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: log10 x + log10 (x+21)=2 1og10[x(x+21)=2 x^2+21x=2 x^2+21x-2=0      Log On


   

Question 544976: log10 x + log10 (x+21)=2
1og10[x(x+21)=2
x^2+21x=2
x^2+21x-2=0
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
log10 x + log10 (x+21)=2
1og10[x(x+21)=2
That means x(x+21) = 10^2
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x^2+21x-100 = 0
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x^2+25x-4x-100 = 0
x(x+25)-4(x+25) = 0
(x+25)(x-4) = 0
Acceptable answer:
x = 4
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Cheers,
Stan H.
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