Tham KY's answer to Xiaoyang's Junior College 1 H2 Maths question.
How do u find the coeff of x^n? :0 is there a formula or ?
From maclaurin expansion, then simplify the factorial, plus a bit of observation...
You start by using the Maclaurin expansion first. Then simplify the n(n-1)(n-2)... with the r! factorial.
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