Problem

35
Solve for $x$ :
\[
\log (x)+\log (x+2)=2
\]

Answer

Expert–verified
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Answer

\(\boxed{x = -1 + \sqrt{101}}\) is the only solution

Steps

Step 1 :\(\log (x(x+2))=2\)

Step 2 :\(\log (x^2+2x)=2\)

Step 3 :\(10^2 = x^2 + 2x\)

Step 4 :\(100 = x^2 + 2x\)

Step 5 :\(x^2 + 2x - 100 = 0\)

Step 6 :\(x = \frac{-2 \pm \sqrt{(2)^2 - 4(1)(-100)}}{2(1)}\)

Step 7 :\(x = \frac{-2 \pm \sqrt{4 + 400}}{2}\)

Step 8 :\(x = \frac{-2 \pm \sqrt{404}}{2}\)

Step 9 :\(x = -1 \pm \sqrt{101}\)

Step 10 :Check the solutions in the original equation

Step 11 :\(x = -1 + \sqrt{101}\) is a valid solution

Step 12 :\(x = -1 - \sqrt{101}\) is not a valid solution

Step 13 :\(\boxed{x = -1 + \sqrt{101}}\) is the only solution

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