We want to expand (2x + y²)⁵.
From Pascal's Triangle (shown below), the coefficients of the expansion are
1,5,10,10,5,1.
n=0: 1
n=1: 1 1
n=2: 1 2 1
n=3: 1 3 3 1
n=4: 1 4 6 4 1
n=5: 1 5 10 10 5 1
Therefore the third term in the expansion is
10*(2x)³*(y²)² = 10*(8x³)*(y⁴) = 80x³y⁴
Alternatively, the third term is
₅C₃ (2x)³(y²)² = 10*(8x³)*(y⁴) = 80x³y⁴
Answer: 80x³y⁴
