AQA FP3 2010 June — Question 3 7 marks

Exam BoardAQA
ModuleFP3 (Further Pure Mathematics 3)
Year2010
SessionJune
Marks7
PaperDownload PDF ↗
TopicIntegration with Partial Fractions
TypeImproper integrals with infinite upper limit (exponential/IBP)
DifficultyStandard +0.3 This is a straightforward Further Maths improper integral question requiring standard integration by parts followed by routine limit evaluation. Part (a) tests definition recall, part (b) is a textbook integration by parts example, and part (c) applies a standard limiting process. While it's Further Maths content, the techniques are mechanical with no novel insight required, making it slightly easier than average overall.
Spec1.08i Integration by parts4.08c Improper integrals: infinite limits or discontinuous integrands

3
  1. Explain why \(\int _ { 1 } ^ { \infty } 4 x \mathrm { e } ^ { - 4 x } \mathrm {~d} x\) is an improper integral.
  2. Find \(\quad \int 4 x \mathrm { e } ^ { - 4 x } \mathrm {~d} x\).
  3. Hence evaluate \(\int _ { 1 } ^ { \infty } 4 x \mathrm { e } ^ { - 4 x } \mathrm {~d} x\), showing the limiting process used.

3
\begin{enumerate}[label=(\alph*)]
\item Explain why $\int _ { 1 } ^ { \infty } 4 x \mathrm { e } ^ { - 4 x } \mathrm {~d} x$ is an improper integral.
\item Find $\quad \int 4 x \mathrm { e } ^ { - 4 x } \mathrm {~d} x$.
\item Hence evaluate $\int _ { 1 } ^ { \infty } 4 x \mathrm { e } ^ { - 4 x } \mathrm {~d} x$, showing the limiting process used.
\end{enumerate}

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