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Evaluate the integral.

int4x^(2)ln(-4x)dx
Answer:

Evaluate the integral.\newline4x2ln(4x)dx \int 4 x^{2} \ln (-4 x) d x \newlineAnswer:

Full solution

Q. Evaluate the integral.\newline4x2ln(4x)dx \int 4 x^{2} \ln (-4 x) d x \newlineAnswer:
  1. Choose uu and dvdv: Let's use integration by parts to solve the integral 4x2ln(4x)dx\int 4x^2\ln(-4x)\,dx. Integration by parts is given by udv=uvvdu\int u\,dv = uv - \int v\,du, where we need to choose uu and dvdv such that dudu and vv are easily computable. Let's choose u=ln(4x)u = \ln(-4x) and dv=4x2dxdv = 4x^2\,dx. Then we need to compute dudu and vv.
  2. Compute du: First, we compute du by differentiating u with respect to x. Since u=ln(4x)u = \ln(-4x), dudx=1(4x)×(4)=1x\frac{du}{dx} = \frac{1}{(-4x)} \times (-4) = -\frac{1}{x}. Therefore, du=dxxdu = -\frac{dx}{x}.
  3. Compute vv: Next, we compute vv by integrating dvdv. Since dv=4x2dxdv = 4x^2dx, v=4x2dxv = \int 4x^2dx. To integrate x2x^2, we use the power rule xndx=x(n+1)/(n+1)\int x^n dx = x^{(n+1)}/(n+1) for n1n \neq -1. Thus, v=4x3/3v = 4x^3/3.
  4. Apply integration by parts: Now we apply the integration by parts formula: udv=uvvdu\int u\,dv = uv - \int v\,du. Substituting uu, dudu, vv, and dvdv, we get 4x2ln(4x)dx=ln(4x)(4x33)(4x33)(dxx)\int 4x^2\ln(-4x)\,dx = \ln(-4x) \cdot \left(\frac{4x^3}{3}\right) - \int\left(\frac{4x^3}{3}\right) \cdot \left(-\frac{dx}{x}\right).
  5. Simplify the integral: Simplify the integral on the right: (4x33)(dxx)=43x2dx\int\left(\frac{4x^3}{3}\right) * \left(-\frac{dx}{x}\right) = -\frac{4}{3} \int x^2dx. Again, we use the power rule for integration to find x2dx=x33\int x^2dx = \frac{x^3}{3}.
  6. Perform the integration: Perform the integration: 43x2dx=43(x33)=4x39.-\frac{4}{3} \int x^2 \, dx = -\frac{4}{3} \cdot \left(\frac{x^3}{3}\right) = -\frac{4x^3}{9}.
  7. Write down full expression: Now we have all the parts to write down the full expression for the integral: 4x2ln(4x)dx=ln(4x)(4x33)(4x39)\int 4x^2\ln(-4x)\,dx = \ln(-4x) \cdot \left(\frac{4x^3}{3}\right) - \left(-\frac{4x^3}{9}\right).
  8. Simplify the expression: Simplify the expression: ln(4x)×(4x33)(4x39)=(4x33)ln(4x)+4x39.\ln(-4x) \times \left(\frac{4x^3}{3}\right) - \left(-\frac{4x^3}{9}\right) = \left(\frac{4x^3}{3}\right)\ln(-4x) + \frac{4x^3}{9}.
  9. Add constant of integration: Finally, we add the constant of integration CC to our result to get the indefinite integral: 4x2ln(4x)dx=(4x33)ln(4x)+4x39+C\int 4x^2\ln(-4x)\,dx = \left(\frac{4x^3}{3}\right)\ln(-4x) + \frac{4x^3}{9} + C.