Question

a) 7C₂ =(Simplify your answer.)

Answer 1

This is a combination of the form:

$\begin{gathered} C(n,k)=nCk=\frac{n!}{k!(n-k)!} \\ where: \\ n>k \end{gathered}$

So:

$7C_2=\frac{7!}{2!(7-2)!}=\frac{7!}{2!\cdot5!}=\frac{5040}{2\cdot120}=\frac{5040}{240}=21$

Answer:

21