OCR C4 2011 June — Question 1 4 marks

Exam BoardOCR
ModuleC4 (Core Mathematics 4)
Year2011
SessionJune
Marks4
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicPolynomial Division & Manipulation
TypeSimple Algebraic Fraction Simplification
DifficultyModerate -0.3 This is a straightforward algebraic fraction simplification requiring factorization of both numerator and denominator, then canceling common factors. The numerator factors as a quadratic in x² (difference of squares twice), and the denominator quadratics are already given. While it requires careful algebraic manipulation across multiple steps, it's a standard C4 technique with no novel problem-solving required, making it slightly easier than average.
Spec1.02k Simplify rational expressions: factorising, cancelling, algebraic division

1 Simplify \(\frac { x ^ { 4 } - 10 x ^ { 2 } + 9 } { \left( x ^ { 2 } - 2 x - 3 \right) \left( x ^ { 2 } + 8 x + 15 \right) }\).

Question 1:
AnswerMarks Guidance
Answer/WorkingMarks Guidance
Attempt to factorise both numerator & denominatorM1 completely or partially
Num = e.g. \((x^2-1)(x^2-9)\) or \((x^2-2x-3)(x^2+2x-3)\)B1 or \((x-3)(x+3)(x-1)(x+1)\)
Denominator = e.g. \((x^2-2x-3)(x+5)(x+3)\)B1 or \((x-3)(x+1)(x+5)(x+3)\)
\(\frac{x-1}{x+5}\) or \(1-\frac{6}{x+5}\) WWWA1 4 ISW but not if any further 'cancellation'
Alternative: long division
Expand denom as quartic & attempt to divide \(\frac{\text{numerator}}{\text{denominator}}\)M1 but not divide \(\frac{\text{denominator}}{\text{numerator}}\)
Obtain quotient = 1 & remainder = \(-6x^3-6x^2+54x+54\)B1
Final B1 A1 available as before
# Question 1:

| Answer/Working | Marks | Guidance |
|---|---|---|
| Attempt to factorise **both** numerator & denominator | M1 | completely or partially |
| Num = e.g. $(x^2-1)(x^2-9)$ or $(x^2-2x-3)(x^2+2x-3)$ | B1 | or $(x-3)(x+3)(x-1)(x+1)$ |
| Denominator = e.g. $(x^2-2x-3)(x+5)(x+3)$ | B1 | or $(x-3)(x+1)(x+5)(x+3)$ |
| $\frac{x-1}{x+5}$ or $1-\frac{6}{x+5}$ WWW | A1 **4** | ISW but not if any further 'cancellation' |
| **Alternative: long division** | | |
| Expand denom as quartic & attempt to divide $\frac{\text{numerator}}{\text{denominator}}$ | M1 | but not divide $\frac{\text{denominator}}{\text{numerator}}$ |
| Obtain quotient = 1 & remainder = $-6x^3-6x^2+54x+54$ | B1 | |
| Final B1 A1 available as before | | |

---
1 Simplify $\frac { x ^ { 4 } - 10 x ^ { 2 } + 9 } { \left( x ^ { 2 } - 2 x - 3 \right) \left( x ^ { 2 } + 8 x + 15 \right) }$.

\hfill \mbox{\textit{OCR C4 2011 Q1 [4]}}