CAIE P3 2019 March — Question 4 5 marks

Exam BoardCAIE
ModuleP3 (Pure Mathematics 3)
Year2019
SessionMarch
Marks5
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicIntegration by Parts
TypeIntegration of x^n·ln(x)
DifficultyStandard +0.3 This is a straightforward integration by parts question with a standard form (x^n·ln(x)). The technique is routine for P3 level: let u=ln(x) and dv=x^(-3/2)dx, integrate by parts, then evaluate definite integral limits. The fractional power and logarithm evaluation require care but follow standard procedures, making it slightly easier than average.
Spec1.07l Derivative of ln(x): and related functions1.08i Integration by parts

4 Show that \(\int _ { 1 } ^ { 4 } x ^ { - \frac { 3 } { 2 } } \ln x \mathrm {~d} x = 2 - \ln 4\).

Question 4:
AnswerMarks Guidance
AnswerMark Guidance
Integrate by parts and reach \(ax^{-\frac{1}{2}}\ln x + b\int x^{-\frac{1}{2}}\cdot\frac{1}{x}\,dx\)M1*
Obtain \(-2x^{-\frac{1}{2}}\ln x + 2\int x^{-\frac{3}{2}}\cdot\frac{1}{x}\,dx\), or equivalentA1
Complete the integration, obtaining \(-2x^{-\frac{1}{2}}\ln x - 4x^{-\frac{1}{2}}\), or equivalentA1
Substitute limits correctly, having integrated twiceM1(dep*)
Obtain the given answer following full and correct workingA1
## Question 4:

| Answer | Mark | Guidance |
|--------|------|----------|
| Integrate by parts and reach $ax^{-\frac{1}{2}}\ln x + b\int x^{-\frac{1}{2}}\cdot\frac{1}{x}\,dx$ | M1* | |
| Obtain $-2x^{-\frac{1}{2}}\ln x + 2\int x^{-\frac{3}{2}}\cdot\frac{1}{x}\,dx$, or equivalent | A1 | |
| Complete the integration, obtaining $-2x^{-\frac{1}{2}}\ln x - 4x^{-\frac{1}{2}}$, or equivalent | A1 | |
| Substitute limits correctly, having integrated twice | M1(dep*) | |
| Obtain the given answer following full and correct working | A1 | |
4 Show that $\int _ { 1 } ^ { 4 } x ^ { - \frac { 3 } { 2 } } \ln x \mathrm {~d} x = 2 - \ln 4$.\\

\hfill \mbox{\textit{CAIE P3 2019 Q4 [5]}}