OCR MEI C1 — Question 6 4 marks

Exam BoardOCR MEI
ModuleC1 (Core Mathematics 1)
Marks4
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicBinomial Theorem (positive integer n)
TypeStandard binomial expansion coefficient
DifficultyModerate -0.8 This is a straightforward application of the binomial theorem requiring identification of the correct term and calculation of one coefficient. It's easier than average as it involves only substitution into the binomial formula with small numbers and no algebraic manipulation beyond the expansion itself.
Spec1.04a Binomial expansion: (a+b)^n for positive integer n
6 Find the coefficient of \(x ^ { 2 }\) in the expansion of \(( 3 - 2 x ) ^ { 5 }\).
Question 6:
AnswerMarks Guidance
\((3-2x)^5 = 3^5 - 5 \cdot 3^4 \cdot 2x + 10 \cdot 3^3 \cdot (2x)^2 - \ldots\)M1 A1 Binomial expansion, Coefficient 10
\(\Rightarrow\) 3rd term is \(10 \times 27 \times 4x^2 = 1080x^2\)A1 A1 Powers (\(3^3\) and \(2^2\)), c.a.o 
## Question 6:
$(3-2x)^5 = 3^5 - 5 \cdot 3^4 \cdot 2x + 10 \cdot 3^3 \cdot (2x)^2 - \ldots$ | M1 A1 | Binomial expansion, Coefficient 10
$\Rightarrow$ 3rd term is $10 \times 27 \times 4x^2 = 1080x^2$ | A1 A1 | Powers ($3^3$ and $2^2$), c.a.o

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6 Find the coefficient of $x ^ { 2 }$ in the expansion of $( 3 - 2 x ) ^ { 5 }$.

\hfill \mbox{\textit{OCR MEI C1  Q6 [4]}}
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