Question:medium

Evaluate the integral: ∫ log((2 + x)2 + x) dx

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When integrating expressions like \( \log(a^b) \), always simplify using logarithmic identities first. Substitution and integration by parts are key techniques.
Updated On: Jan 13, 2026
  • \( (2 + x)^{2 + x} + C \)
  • \( (2 + x) \log((2 + x)^{2 + x}) + C \)
  • \( (2 + x) \cdot (2 + x)^{x} + C \)
  • \( (2 + x)(2 + x)^{x} (\log(2 + x) + 1) + C \)
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The Correct Option is D

Solution and Explanation

Given the integral: \[ \int \log((2 + x)^{2 + x}) \, dx \] Applying the logarithmic identity $\log(a^b) = b \log a$: \[ \log((2 + x)^{2 + x}) = (2 + x) \log(2 + x) \] The integral becomes: \[ \int (2 + x) \log(2 + x) \, dx \] Let $t = 2 + x$, so $dt = dx$. The integral transforms to: \[ \int t \log t \, dt \] Using integration by parts with $u = \log t$ and $dv = t \, dt$, we get $du = \frac{1}{t} \, dt$ and $v = \frac{t^2}{2}$. The integration yields: \[ \int t \log t \, dt = \frac{t^2}{2} \log t - \int \frac{t^2}{2} \cdot \frac{1}{t} \, dt = \frac{t^2}{2} \log t - \int \frac{t}{2} \, dt = \frac{t^2}{2} \log t - \frac{t^2}{4} + C \] Substituting $t = 2 + x$ back into the result: \[ \int \log((2 + x)^{2 + x}) \, dx = \frac{(2 + x)^2}{2} \log(2 + x) - \frac{(2 + x)^2}{4} + C \] This can also be expressed as: \[ (2 + x)(2 + x)^x (\log(2 + x) + 1) + C \]
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