CPM Homework Help : CCA2 Problem 12-82

What is the fifth term of each expansion?

$(a + b)^9$
Hint (a):
Review the Math Notes box in Lesson 10.3.1.
If you are looking for the fifth term, what will the exponents of $a$ and $b$ be?

$(2x + y)^8$
Hint (b):
Use the same method as part (a).
Answer (b):
$1120x^4y^4$