(2x² + y²)⁴
By Binomial Expansion:
⁴C₀(2x²)⁴(y²)⁰ + ⁴C₁(2x²)³(y²)¹ + ⁴C₂(2x²)²(y²)² + ⁴C₃(2x²)¹(y²)³ + ⁴C₄(2x²)⁰(y²)⁴
From Pascal's Triangle:
Note the C is the values from Combinations.
For power 4, the factors are:
1 , 4, 6, 4, 1
1*(2x²)⁴(y²)⁰ + 4*(2x²)³(y²)¹ + 6*(2x²)²(y²)² + 4*(2x²)¹(y²)³ + 1*(2x²)⁰(y²)⁴
Note if it raised to power zero = 1.
(2⁴x² ˣ ⁴) + 4*2³x² ˣ ³y² ˣ ¹ + 6*2²x² ˣ ² y² ˣ ² + 4*2x² ˣ ¹y² ˣ ³ + y² ˣ ⁴
16x⁸ + 32x⁶y² + 24x⁴y⁴ + 8x²y⁶ + y⁸
I hope this helped.