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Evaluate the integral.

int6x^(2)2^(3x)dx
Answer:

Evaluate the integral.\newline6x223xdx \int 6 x^{2} 2^{3 x} d x \newlineAnswer:

Full solution

Q. Evaluate the integral.\newline6x223xdx \int 6 x^{2} 2^{3 x} d x \newlineAnswer:
  1. Identify integral: Identify the integral to be solved.\newlineWe need to evaluate the integral of the function 6x223x6x^2 \cdot 2^{3x} with respect to xx.\newlineI=6x223xdxI = \int 6x^2 \cdot 2^{3x} \, dx
  2. Recognize integral type: Recognize that the integral involves a product of a polynomial and an exponential function.\newlineThis integral does not have a straightforward antiderivative, so we will need to use integration by parts.\newlineIntegration by parts formula: udv=uvvdu\int u \, dv = uv - \int v \, du
  3. Choose uu and dvdv: Choose uu and dvdv. Let u=6x2u = 6x^2 (which will become simpler when differentiated) and dv=23xdxdv = 2^{3x} dx (which will remain the same when integrated).
  4. Differentiate and integrate: Differentiate uu and integrate dvdv.
    du=d(6x2)=12xdxdu = d(6x^2) = 12x \, dx
    v=2(3x)dxv = \int 2^{(3x)} \, dx
    To integrate vv, we need to use the fact that a(f(x))f(x)dx=a(f(x))ln(a)+C\int a^{(f(x))} f'(x) \, dx = \frac{a^{(f(x))}}{\ln(a)} + C, where aa is a constant and f(x)f(x) is a function of xx.
  5. Integrate dvdv to find vv: Integrate dvdv to find vv.v=2(3x)dx=2(3x)3ln(2)+Cv = \int 2^{(3x)} \, dx = \frac{2^{(3x)}}{3\ln(2)} + C
  6. Apply integration by parts: Apply the integration by parts formula.\newlineI=uvvduI = uv - \int v \, du\newlineI=(6x2)(23x3ln(2))(23x3ln(2))(12x)dxI = (6x^2) \cdot \left(\frac{2^{3x}}{3\ln(2)}\right) - \int \left(\frac{2^{3x}}{3\ln(2)}\right) \cdot (12x) \, dx
  7. Simplify the expression: Simplify the expression.\newlineI=2x223xln(2)4ln(2)x23xdxI = \frac{2x^2 \cdot 2^{3x}}{\ln(2)} - \frac{4}{\ln(2)} \cdot \int x \cdot 2^{3x} dx\newlineNow we have a new integral to solve, which is again a product of a polynomial and an exponential function.
  8. Apply integration by parts again: Apply integration by parts to the new integral.\newlineLet u=xu = x and dv=23xdxdv = 2^{3x} dx for the new integral.\newlinedu=dxdu = dx\newlinev=23xdx=23x3ln(2)+Cv = \int 2^{3x} dx = \frac{2^{3x}}{3\ln(2)} + C (as calculated before)
  9. Integrate new integral: Apply the integration by parts formula to the new integral.\newlineInew=uvvduI_{\text{new}} = uv - \int v \, du\newlineInew=x(23x3ln(2))(23x3ln(2))dxI_{\text{new}} = x \cdot \left(\frac{2^{3x}}{3\ln(2)}\right) - \int \left(\frac{2^{3x}}{3\ln(2)}\right) \, dx
  10. Apply integration by parts to new integral: Integrate the remaining integral.\newline23x3ln(2)dx=23x9ln(2)2+C\int \frac{2^{3x}}{3\ln(2)} \, dx = \frac{2^{3x}}{9\ln(2)^2} + C
  11. Integrate remaining integral: Substitute InewI_{\text{new}} back into the original integral.I=(2x223xln(2))(4ln(2))(x(23x3ln(2))(23x9ln(2)2))I = \left(\frac{2x^2 \cdot 2^{3x}}{\ln(2)}\right) - \left(\frac{4}{\ln(2)}\right) \cdot \left(x \cdot \left(\frac{2^{3x}}{3\ln(2)}\right) - \left(\frac{2^{3x}}{9\ln(2)^2}\right)\right)
  12. Substitute InewI_{\text{new}}: Simplify the expression.I=2x223xln(2)4x23x3ln(2)2+423x9ln(2)3+CI = \frac{2x^2 \cdot 2^{3x}}{\ln(2)} - \frac{4x \cdot 2^{3x}}{3\ln(2)^2} + \frac{4 \cdot 2^{3x}}{9\ln(2)^3} + C
  13. Simplify the expression: Combine the terms and write the final answer.\newlineI=2x223xln(2)4x23x3ln(2)2+423x9ln(2)3+CI = \frac{2x^2 \cdot 2^{3x}}{\ln(2)} - \frac{4x \cdot 2^{3x}}{3\ln(2)^2} + \frac{4 \cdot 2^{3x}}{9\ln(2)^3} + C

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