Use the formula
(nr)=n!r! (n−r)!\binom{n}{r} = \dfrac{n!}{r!\,(n-r)!}(rn)=r!(n−r)!n!
to show that (104)=210\binom{10}{4} = 210(410)=210.
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Markscheme
1.4.1 Sequences and Series - The Binomial Theorem Questions
108 exam-style questions on WJEC A Level Maths 1.4.1 Sequences and Series - The Binomial Theorem. Each one has a worked solution and a mark scheme showing where the marks go.