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Evaluate the integral.

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

Evaluate the integral.\newlinexe2xdx \int-x e^{-2 x} d x \newlineAnswer:

Full solution

Q. Evaluate the integral.\newlinexe2xdx \int-x e^{-2 x} d x \newlineAnswer:
  1. Use Integration by Parts: Let's use integration by parts to solve the integral of xe2x-xe^{-2x} with respect to xx. Integration by parts is given by the formula udv=uvvdu\int u \, dv = uv - \int v \, du, where uu and dvdv are parts of the integrand that we choose. We will let u=xu = -x and dv=e2xdxdv = e^{-2x}dx. Then we need to find dudu and vv.
  2. Find dudu: First, we differentiate uu to find dudu. Since u=xu = -x, we have du=dxdu = -dx.
  3. Find vv: Next, we integrate dvdv to find vv. Since dv=e2xdxdv = e^{-2x}dx, we have v=e2xdxv = \int e^{-2x}dx. To integrate e2xe^{-2x}, we use the fact that eaxdx=1aeax+C\int e^{ax}dx = \frac{1}{a}e^{ax} + C, where aa is a constant. Therefore, v=(12)e2xv = (-\frac{1}{2})e^{-2x}.
  4. Apply Integration by Parts Formula: Now we apply the integration by parts formula: udv=uvvdu\int u \, dv = uv - \int v \, du. Substituting the values we found, we get xe2xdx=uvvdu=(x)(12)e2x(12)e2x(dx)\int -xe^{-2x}\,dx = uv - \int v \, du = (-x)(-\frac{1}{2})e^{-2x} - \int (-\frac{1}{2})e^{-2x}(-dx).
  5. Simplify the Integral: Simplify the integral: xe2xdx=12xe2x12e2xdx\int -xe^{-2x}\,dx = \frac{1}{2}xe^{-2x} - \int \frac{1}{2}e^{-2x}\,dx.
  6. Integrate (1/2)e2x(1/2)e^{-2x}: Now we need to integrate (1/2)e2x(1/2)e^{-2x} with respect to xx. As before, we use the fact that eaxdx=(1/a)eax+C\int e^{ax}\,dx = (1/a)e^{ax} + C. So, (1/2)e2xdx=(1/2)(1/2)e2x=(1/4)e2x+C\int(1/2)e^{-2x}\,dx = (1/2)(-1/2)e^{-2x} = (-1/4)e^{-2x} + C.
  7. Combine Terms: Combine the terms to get the final answer: xe2xdx=(12)xe2x(14e2x+C)\int -xe^{-2x}\,dx = \left(\frac{1}{2}\right)xe^{-2x} - \left(\frac{-1}{4}e^{-2x} + C\right).
  8. Final Answer: Simplify the expression to get the final answer: xe2xdx=(12)xe2x+(14)e2x+C\int -xe^{-2x}dx = \left(\frac{1}{2}\right)xe^{-2x} + \left(\frac{1}{4}\right)e^{-2x} + C.