RI/2021/JC1/Promo/P1/Q05

(i) Using standard series from the List of Formulae (MF26), expand $\frac{\cos 3 x}{4-x}$ as far as the term in $x^3$. Give the coefficients as exact fractions in their simplest form.

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(ii) It is given that the third and fourth terms found in part (i) are equal to the third and fourth terms in the series expansion of $(a+b x)^5$, in ascending powers of $x$, respectively. Find the values of the constants $a$ and $b$.

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