Question 679923: solve for x
ln x + ln(x+4)=0
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! ln x + ln(x+4)=0
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ln[x(x+4)] = 0
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x(x+4) = 10^0
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x^2+4x = 1
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x^2+4x-1 = 0
Use the quadratic formula:
x = [-4 +- sqrt(16-4*(-1)]/2
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x = [-4 +- sqrt(20)]/2
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x = [-2 +- 2sqrt(5)]
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Positive solution:
x = -2 + 2sqrt(5) = 2.4721...
Cheers,
Stan H.
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