Answer:
9x^4 + 2x²y² + y^4
Arrange the terms
9x^4 + y^4 + 2x²y²
making the first two terms into a² + b²
(3x²)² + (y²)² + 2x²y²
use the formula of a² + b² = (a+b)² - 2ab
(3x² + y²)² - 2.3x².y² + 2x²y²
(3x² + y²)² - 6x²y² + 2x²y²
(3x² + y²)² - 4x²y²
(3x² + y²)² - (2xy)²
use the formula a² - b²
(3x² + 2xy + y²) (3x² - 2xy + y²)
Explanation: