Evaluate \(\int_{-1}^{1} (x + 1)^{2}\mathrm {d} x\).

  • A \(\frac{8}{3}\)
  • B \(\frac{7}{3}\)
  • C \(\frac{5}{3}\)
  • D 2
waec 2018furthermathematics

The correct answer is A. \(\frac{8}{3}\)

\(\int_{-1}^{1} (x + 1)^{2}\mathrm {d} x \equiv \int_{-1}^{1} (x^{2} + 2x + 1)\mathrm {d} x\)

= \(\left. \frac{x^{3}}{3} + x^{2} + x \right |_{-1}^{1}\)

= \((\frac{1^{3}}{3} + 1^{2} + 1) - (\frac{(-1)^{3}}{3} + (-1)^{2} + (-1)) = \frac{7}{3} + \frac{1}{3} = \frac{8}{3}\)

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