We want to find the fourth term of the expansion of the given expression.
( c+ 6)^8To do so we will use the Binomial Theorem to write the expansion in sigma notation.
(a+b)^n=∑_(k=0)^n n!/k!(n-k)!a^(n-k)b^k
For our expression we have that a= c, b= 6, and n= 8. Since k starts at 0, for the fourth term we have k=3. Remember that we do not have to find the sum — we only need to find one of the terms. Therefore, we will only consider the argument of the summation notation instead of the entire sum.
