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Evaluate the integral.

int-2xe^(3x+2)dx
Answer:

Evaluate the integral.\newline2xe3x+2dx \int-2 x e^{3 x+2} d x \newlineAnswer:

Full solution

Q. Evaluate the integral.\newline2xe3x+2dx \int-2 x e^{3 x+2} d x \newlineAnswer:
  1. Identify Integral: Let's start by identifying the integral we need to evaluate:\newlineI=2xe(3x+2)dxI = \int -2xe^{(3x+2)}\,dx\newlineWe can use integration by parts, which states that udv=uvvdu\int u\, dv = uv - \int v\, du, where uu and dvdv are parts of the integrand we choose to differentiate and integrate, respectively.\newlineLet's choose u=2xu = -2x (which will be differentiated) and dv=e(3x+2)dxdv = e^{(3x+2)}\,dx (which will be integrated).
  2. Choose uu and dvdv: Differentiate uu with respect to xx to find dudu:
    u=2xu = -2x
    dudx=2\frac{du}{dx} = -2
    du=2dxdu = -2dx
  3. Differentiate uu: Integrate dvdv with respect to xx to find vv:
    dv=e(3x+2)dxdv = e^{(3x+2)}dx
    To integrate e(3x+2)e^{(3x+2)}, we need to use the substitution method. Let w=3x+2w = 3x+2, then dwdx=3\frac{dw}{dx} = 3, dx=dw3dx = \frac{dw}{3}.
    v=e(3x+2)dx=ew(dw3)=(13)ew+Cv = \int e^{(3x+2)}dx = \int e^w \cdot \left(\frac{dw}{3}\right) = \left(\frac{1}{3}\right)e^w + C
    Substitute back w=3x+2w = 3x+2:
    dvdv11
  4. Integrate dv: Now apply the integration by parts formula:\newlineI=uvvduI = uv - \int v du\newlineI=(2x)(13)e(3x+2)(13)e(3x+2)(2dx)I = (-2x)(\frac{1}{3})e^{(3x+2)} - \int (\frac{1}{3})e^{(3x+2)}(-2dx)\newlineI=(23)xe(3x+2)+(23)e(3x+2)dxI = (-\frac{2}{3})xe^{(3x+2)} + (\frac{2}{3})\int e^{(3x+2)}dx
  5. Apply Integration by Parts: We have already found the integral of e3x+2dxe^{3x+2}\,dx when we calculated vv, so we can use that result:\newlineI=(23)xe3x+2+(23)(13e3x+2)+CI = \left(-\frac{2}{3}\right)xe^{3x+2} + \left(\frac{2}{3}\right)\left(\frac{1}{3}e^{3x+2}\right) + C\newlineI=(23)xe3x+2+(29)e3x+2+CI = \left(-\frac{2}{3}\right)xe^{3x+2} + \left(\frac{2}{9}\right)e^{3x+2} + C
  6. Use Result for Integral: Combine the terms with the common factor e3x+2e^{3x+2}:I=e3x+2(23x+29)+CI = e^{3x+2}\left(\frac{-2}{3}x + \frac{2}{9}\right) + C
  7. Combine Terms: Simplify the expression inside the parentheses:\newlineI=e(3x+2)(69x+29)+CI = e^{(3x+2)}\left(\frac{-6}{9}x + \frac{2}{9}\right) + C\newlineI=e(3x+2)(6x+29)+CI = e^{(3x+2)}\left(\frac{-6x + 2}{9}\right) + C
  8. Simplify Expression: Factor out the common factor of 19\frac{1}{9}:I=(19)e(3x+2)(6x+2)+CI = \left(\frac{1}{9}\right)e^{(3x+2)}(-6x + 2) + C