Binomial Theoram is one chapter in which you see a question and then realise that it can easily be done in 2 or 3 ways. Definitely one of the most interesting chapters which uses concepts from calculus, trignometry, complex number prognessiong and wkhat not Binomial theoram finds use in number theory as well. So, let us prober deeper into this section.
Definition of Bionomial theoram
If n is a +ve integer and x1 y are 2 complex number then .
(x + y)n n Cr xn-r yr
= nCoXn - nC1 Xn-1 y + nC2 Xn-2 y2 +............+ n Cn yn
Similarly (x - y) n = nCoXn - nC1 Xn-1 y + nC2 Xn-2 y2 +.......+ (-1) n n Cn yn
The oefficients n Co, nC1, .................nCn are called Bionomial coeff.
are called Bionomial coeff.
Some important facts
(i) There are (n + 1) tevms in the expression .
(ii) lthe sum of in dices. Of x and y in each term of expansion is n .
(iii) The bionomial 3efficent of the terms equidistant from begining and the end are equal .
(iv) The r-th term from end in (x + y)
= (h + r + 2) th term from beginning .
In the expansion of (x + y)n the (r + 1tn) term from beginning of expansion is
Tr + 1 = nCr an-r bb
Expand by biobomial theoram .
Ans T7 from end of (a + b)n is same as T7 from beginning of (b + a)n
of (a + b)n
or ( 2 1/3 3 1/3 ) n - 12 =
So, n = 9