which equation is equivalent to x^4-y^4
x⁴ - y⁴x⁴ - x²y² + x²y² - y⁴x²(x²) - x²(y²) + y²(x²) - y²(y²)x²(x² - y²) + y²(x² - y²)(x² + y²)(x² - y²)