If \(I_{m, n}=\int e^{m x} \cdot x^n d x\), then \(I_{m, n}+\frac{n}{m} I_{m, n-1}=\)

If \(I_{m, n}=\int e^{m x} \cdot x^n d x\), then \(I_{m, n}+\frac{n}{m} I_{m, n-1}=\)
  1. \(x^n \cdot e^{m x}+c\)
  2. \(\frac{x^n e^{m x}}{n}+c\)
  3. \(\frac{x^n \cdot e^{m x}}{m}+c\)
  4. \(\frac{-x^n \cdot e^{m x}}{m}+c\)

Solution

\(\begin{aligned} & \because I_{m, n}=\int e^{m x} \cdot x^n d x \\ & =\frac{1}{m} x^n e^{m x}-\int\left(n x^{n-1}\right)\left(\frac{e^{m x}}{m}\right) d x \\ & =\frac{x^n e^{m x}}{m}-\frac{n}{m} \int e^{m x} x^{n-1} d x=\frac{x^n e^{m x}}{m}-\frac{n}{m} I_{m, n-1}+c \\ & \Rightarrow I_{m, n}+\frac{n}{m} I_{m, n-1}=\frac{x^n e^{m x}}{m}+c \end{aligned}\) Hence, option (c) is correct.

Asked in: AP EAMCET 2019 (23 Apr Shift 1)

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