random post

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let $f(x) = (2+ke^x)^3$, where $k$ is a real constant.

(a) Express, in terms of $k$, the coefficient of $x$ and the coefficient of $x^2$ in the expansion of $f(x)$.

(b) If the coefficient of $x$ in the expansion of $f(x)$ is $-9$, find the value of the coefficient of $x^2$ in this expansion.

($4 +3$ marks)

Worked Solution