10. The binomial expansion, in ascending powers of \(x\), of \(( 1 + k x ) ^ { n }\) is
$$1 + 36 x + 126 k x ^ { 2 } + \ldots$$
where \(k\) is a non-zero constant and \(n\) is a positive integer.
a) Show that \(n k ( n - 1 ) = 252\)
b) Find the value of \(k\) and the value of \(n\).
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