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Integration techniques

Repeated and tabular integration by parts

Material by the IntegralPaso project. Conditions and limits are stated in each guide; external teaching review is pending.

∫P(x)eax dx\int P(x)e^{ax}\,dx

If repeated polynomial differentiation reaches zero, organize derivatives and primitives of the other factor in a table with alternating signs. The table summarizes repeated applications of the same formula.

Common mistake

Keep alternating signs and every exponential factor.

Step-by-step example

  1. Differentiate the polynomial to zero.

    x2, 2x, 2, 0x^2,\ 2x,\ 2,\ 0
  2. Integrate eˣ repeatedly and alternate signs.

    ex(x2)−ex(2x)+ex(2)e^x(x^2)-e^x(2x)+e^x(2)
  3. Add C and check by differentiating.

    ∫x2ex dx=ex(x2−2x+2)+C\int x^2e^x\,dx=e^x(x^2-2x+2)+C
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