CAIE P2 2011 June — Question 4 5 marks

Exam BoardCAIE
ModuleP2 (Pure Mathematics 2)
Year2011
SessionJune
Marks5
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicPolynomial Division & Manipulation
TypeFinding Constants from Factor or Zero Remainder Conditions
DifficultyModerate -0.8 This is a straightforward application of the factor theorem and polynomial division. Part (i) requires substituting x=-2 and solving a linear equation for a. Part (ii) is routine polynomial division or synthetic division with no conceptual challenges. Both parts are standard textbook exercises requiring only direct application of well-practiced techniques.
Spec1.02j Manipulate polynomials: expanding, factorising, division, factor theorem1.02k Simplify rational expressions: factorising, cancelling, algebraic division

4 The polynomial \(\mathrm { f } ( x )\) is defined by $$f ( x ) = 3 x ^ { 3 } + a x ^ { 2 } + a x + a$$ where \(a\) is a constant.
  1. Given that \(( x + 2 )\) is a factor of \(\mathrm { f } ( x )\), find the value of \(a\).
  2. When \(a\) has the value found in part (i), find the quotient when \(\mathrm { f } ( x )\) is divided by ( \(x + 2\) ).

AnswerMarks Guidance
(i) Substitute \(-2\) and equate to zero or divide by \(x + 2\) and equate remainder to zeroM1
Obtain \(a = 8\)A1 [2]
(ii) Attempt to find quotient by division or inspection or use of identityM1
Obtain at least \(3x^2 + 2x\)A1
Obtain \(3x^2 + 2x + 4\) with no errors seenA1 [3]
**(i)** Substitute $-2$ and equate to zero or divide by $x + 2$ and equate remainder to zero | M1 |
Obtain $a = 8$ | A1 | [2]

**(ii)** Attempt to find quotient by division or inspection or use of identity | M1 |
Obtain at least $3x^2 + 2x$ | A1 |
Obtain $3x^2 + 2x + 4$ with no errors seen | A1 | [3]
4 The polynomial $\mathrm { f } ( x )$ is defined by

$$f ( x ) = 3 x ^ { 3 } + a x ^ { 2 } + a x + a$$

where $a$ is a constant.\\
(i) Given that $( x + 2 )$ is a factor of $\mathrm { f } ( x )$, find the value of $a$.\\
(ii) When $a$ has the value found in part (i), find the quotient when $\mathrm { f } ( x )$ is divided by ( $x + 2$ ).

\hfill \mbox{\textit{CAIE P2 2011 Q4 [5]}}