To find: the value of n with respect to the binomial expansion of (a + b)n where the coefficients of the 4th and 13th terms are equal to each other
Formula Used:
A general term, Tr+1 of binomial expansion (x + y)n is given by,
Now, finding the 4th term, we get
T4 = nC3 x an-3 x (b)3
Thus, the coefficient of a 4th term is nC3
Now, finding the 13th term, we get
T13 = nC12 x an-12 x (b)12
Thus, coefficient of 4th term is nC12
As the coefficients are equal, we get
n -12 = 3
n =15
Thus, value of n is 15