We want to find the sixth term of the expansion of the given expression.
( 3x+ 4y)^7To 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= 3x, b= 4y, and n= 7. Since k starts at 0, for the sixth term we have k=5. 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.
