OCR MEI Further Pure Core 2023 June — Question 4 6 marks

Exam BoardOCR MEI
ModuleFurther Pure Core (Further Pure Core)
Year2023
SessionJune
Marks6
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicTaylor series
TypeMaclaurin series for composite exponential/root functions
DifficultyStandard +0.3 This is a straightforward Further Maths question requiring routine differentiation of a composite root function, standard Maclaurin series construction using f(0), f'(0), f''(0), and substitution of x=2 to approximate √5. While it involves multiple steps, each is a standard technique with no novel insight required, making it slightly easier than average even for Further Maths.
Spec4.08a Maclaurin series: find series for function4.08b Standard Maclaurin series: e^x, sin, cos, ln(1+x), (1+x)^n

4
    1. Given that \(\mathrm { f } ( x ) = \sqrt { 1 + 2 x }\), find \(\mathrm { f } ^ { \prime } ( x )\) and \(\mathrm { f } ^ { \prime \prime } ( x )\).
    2. Hence, find the first three terms of the Maclaurin series for \(\sqrt { 1 + 2 x }\).
  1. Hence, using a suitable value for \(x\), show that \(\sqrt { 5 } \approx \frac { 143 } { 64 }\).

Question 4:
AnswerMarks Guidance
4(a) (i)
f′(𝑥)= (1+2𝑥) (cid:2879) (cid:2870)
(cid:2871)
AnswerMarks
f″(𝑥)= −(1+2𝑥) (cid:2879) (cid:2870)B1
B1
AnswerMarks
[2]1.1
1.1
AnswerMarks Guidance
4(a) (ii)
1
1+𝑥− 𝑥(cid:2870)
AnswerMarks
2M1
A1
AnswerMarks
[2]1.1
1.1Their f(0), f’(0) and f’’(0) evaluated and substituted into
Maclaurin
Must come from correct expressions for f ′(𝑥), f ′′(𝑥); cannot
come from binomial expansion. Ignore subsequent terms.
AnswerMarks Guidance
4(b) (cid:2870)
(cid:2869) (cid:2869) (cid:2869) (cid:2869)
(cid:3495)1+2× or 1+ − (cid:4672) (cid:4673)
(cid:2876) (cid:2876) (cid:2870) (cid:2876)
(cid:2869)(cid:2872)(cid:2871)
 √5 ≈
AnswerMarks
(cid:2874)(cid:2872)M1
A1
AnswerMarks
[2]3.1a
2.2a(cid:2869)
using 𝑥 = in their expansion
(cid:2876)
AG
Question 4:
4 | (a) | (i) | (cid:2869)
f′(𝑥)= (1+2𝑥) (cid:2879) (cid:2870)
(cid:2871)
f″(𝑥)= −(1+2𝑥) (cid:2879) (cid:2870) | B1
B1
[2] | 1.1
1.1
4 | (a) | (ii) | f(0)= 1, f(cid:4593)(0)= 1, f(cid:4593)(cid:4593)(0)= −1
1
1+𝑥− 𝑥(cid:2870)
2 | M1
A1
[2] | 1.1
1.1 | Their f(0), f’(0) and f’’(0) evaluated and substituted into
Maclaurin
Must come from correct expressions for f ′(𝑥), f ′′(𝑥); cannot
come from binomial expansion. Ignore subsequent terms.
4 | (b) | (cid:2870)
(cid:2869) (cid:2869) (cid:2869) (cid:2869)
(cid:3495)1+2× or 1+ − (cid:4672) (cid:4673)
(cid:2876) (cid:2876) (cid:2870) (cid:2876)
(cid:2869)(cid:2872)(cid:2871)
 √5 ≈
(cid:2874)(cid:2872) | M1
A1
[2] | 3.1a
2.2a | (cid:2869)
using 𝑥 = in their expansion
(cid:2876)
AG
4
\begin{enumerate}[label=(\alph*)]
\item \begin{enumerate}[label=(\roman*)]
\item Given that $\mathrm { f } ( x ) = \sqrt { 1 + 2 x }$, find $\mathrm { f } ^ { \prime } ( x )$ and $\mathrm { f } ^ { \prime \prime } ( x )$.
\item Hence, find the first three terms of the Maclaurin series for $\sqrt { 1 + 2 x }$.
\end{enumerate}\item Hence, using a suitable value for $x$, show that $\sqrt { 5 } \approx \frac { 143 } { 64 }$.
\end{enumerate}

\hfill \mbox{\textit{OCR MEI Further Pure Core 2023 Q4 [6]}}