Binomial theorem, statement that for any positive integer n, the nth power of the sum of two numbers a and b may be expressed as the sum of n + 1 terms of the form.
To evaluate the combination we proceed as follows: 21C3 Given nCk we shall have: n!/[(n-k)!k!] thus plugging the values in the expression we get: 21!/[(21-3)!3!] =21!/(18!×3!) =1330 Answer: 1330
