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int_(1)^(sqrt5)(2ln(x^(2)+7))/(x^(2)+2)dx

152ln(x2+7)x2+2dx \int_{1}^{\sqrt{5}} \frac{2 \ln \left(x^{2}+7\right)}{x^{2}+2} d x

Full solution

Q. 152ln(x2+7)x2+2dx \int_{1}^{\sqrt{5}} \frac{2 \ln \left(x^{2}+7\right)}{x^{2}+2} d x
  1. Substitution: Let's do a substitution: let u=x2+7u = x^2 + 7. Then du=2xdxdu = 2x \, dx.
  2. Change Limits: Change the limits of integration. When x=1x = 1, u=12+7=8u = 1^2 + 7 = 8. When x=5x = \sqrt{5}, u=(5)2+7=12u = (\sqrt{5})^2 + 7 = 12.
  3. Rewrite Integral: Rewrite the integral in terms of uu: 812ln(u)u2du\int_{8}^{12}\frac{\ln(u)}{u-2} \, du.
  4. Integrate ln(u)/(u2)\ln(u)/(u-2): Now, we need to integrate ln(u)/(u2)\ln(u)/(u-2). This isn't a standard integral, so we might need to use integration by parts.
  5. Integration by Parts: Let's use integration by parts: let v=ln(u)v = \ln(u) and dw=1(u2)dudw = \frac{1}{(u-2)} du. Then dv=1ududv = \frac{1}{u} du and w=ln(u2)w = \ln(u-2).
  6. Apply Integration by Parts: Apply integration by parts: vdw=vwwdv\int v \, dw = vw - \int w \, dv.
  7. Calculate Integral: Calculate the integral: ln(u)ln(u2)ln(u2)(1u)du\ln(u) \cdot \ln(u-2) - \int \ln(u-2) \cdot \left(\frac{1}{u}\right) du.
  8. Correct Mistake: This step is incorrect because the integral of 1(u2)\frac{1}{(u-2)} is not ln(u2)\ln(u-2). The correct antiderivative should be a logarithm with a constant adjustment. We need to correct this mistake.

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