OCR MEI C1 2012 June — Question 4 3 marks

Exam BoardOCR MEI
ModuleC1 (Core Mathematics 1)
Year2012
SessionJune
Marks3
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicPartial Fractions
TypeSimplify algebraic fractions by multiplication or division
DifficultyEasy -1.2 This is a straightforward algebraic manipulation requiring factorisation of two quadratics (difference of squares and standard trinomial) followed by cancellation. It's simpler than average A-level work as it only tests basic factorisation skills with no problem-solving element, though it requires careful execution to avoid errors.
Spec1.02j Manipulate polynomials: expanding, factorising, division, factor theorem1.02k Simplify rational expressions: factorising, cancelling, algebraic division

Factorise and hence simplify the following expression. $$\frac{x^2 - 9}{x^2 + 5x + 6}$$ [3]

AnswerMarks Guidance
\(\frac{x - 3}{x + 2}\) or \(1 - \frac{5}{x + 2}\) as final answer www3 B2 for correct answer seen and then spoilt; M1 for \((x + 3)(x - 3)\) and M1 for \((x + 2)(x + 3)\)
[3]
Question 5(i):
AnswerMarks Guidance
303 M1 for \((\sqrt{6})^6 = 6\sqrt{6}\) soi and M1 for \(\sqrt{24} = 2\sqrt{6}\) soi or allow SC2 for final answer of \(5(\sqrt{6})^2\) or \(5\sqrt{36}\) or \(10\sqrt{9}\) etc
[3]
Question 5(ii):
AnswerMarks Guidance
\(\frac{8}{11}\)2 M1 for common denominator \((4 + \sqrt{5})(4 - \sqrt{5})\) soi - may be in separate fractions or for a final answer with denominator 11, even if worked with only one fraction
[2]
Question 6(i):
AnswerMarks
10 cao[1]
Question 6(ii):
AnswerMarks Guidance
\(-720[x^3]\)4 B3 for \(720[x^3]\) or for \(10 \times 9 \times -8[x^3]\) or M2 for \(10 \times 3^2 \times (-2)^r\) oe or ft from (i) or M1 for two of these three elements correct or ft; condone \(x\) still included
[4]
$\frac{x - 3}{x + 2}$ or $1 - \frac{5}{x + 2}$ as final answer www | 3 | B2 for correct answer seen and then spoilt; M1 for $(x + 3)(x - 3)$ and M1 for $(x + 2)(x + 3)$
| [3] |

# Question 5(i):

30 | 3 | M1 for $(\sqrt{6})^6 = 6\sqrt{6}$ soi and M1 for $\sqrt{24} = 2\sqrt{6}$ soi or allow SC2 for final answer of $5(\sqrt{6})^2$ or $5\sqrt{36}$ or $10\sqrt{9}$ etc | M0 for $6000\sqrt{6}$ ie cubing 10 as well; for those using indices: M1 for both $10 \times 6^{1/2}$ and $2 \times 6^{1/2}$ oe then M1 for $5 \times 6$ oe; award SC2 for similar correct answer with no denominator
| [3] |

# Question 5(ii):

$\frac{8}{11}$ | 2 | M1 for common denominator $(4 + \sqrt{5})(4 - \sqrt{5})$ soi - may be in separate fractions or for a final answer with denominator 11, even if worked with only one fraction | condone lack of brackets
| [2] |

# Question 6(i):

10 cao | [1] |

# Question 6(ii):

$-720[x^3]$ | 4 | B3 for $720[x^3]$ or for $10 \times 9 \times -8[x^3]$ or M2 for $10 \times 3^2 \times (-2)^r$ oe or ft from (i) or M1 for two of these three elements correct or ft; condone $x$ still included | condone $-720 x$ etc; allow equivalent marks for the $x^3$ term as part of a longer expansion eg M2 for $3^r\ldots 10 \times \left(\frac{-2}{3}\right)^r\ldots$ or M1 for $10 \times \left(\frac{-2}{3}\right)^r$ etc
| [4] |
Factorise and hence simplify the following expression.
$$\frac{x^2 - 9}{x^2 + 5x + 6}$$ [3]

\hfill \mbox{\textit{OCR MEI C1 2012 Q4 [3]}}