Easy -1.2 This is a straightforward application of the binomial theorem requiring only substitution into the formula C(6,4) × 5² = 15 × 25 = 375. It's a single-step calculation with no problem-solving required, making it easier than average but not trivial since students must recall and correctly apply the binomial coefficient formula.
Allow \(375x^4\); M1 for \(5^2\) or 25 used or seen with \(x^4\) and M1 for 15 or \(\frac{6\times5}{2}\) oe e.g. \(\frac{6!}{4!2!}\) or 1 6 15 … seen [\(^6C_4\) not sufficient]
## Question 16:
$375$ | **3** | Allow $375x^4$; M1 for $5^2$ or 25 used or seen with $x^4$ and M1 for 15 or $\frac{6\times5}{2}$ oe e.g. $\frac{6!}{4!2!}$ or 1 6 15 … seen [$^6C_4$ not sufficient] | Total: **3**
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