Question

What expressions are equivalent to y4 - 625?

Answer 1

option D

Explanation:

a² - b² = (a + b) (a - b)

625 = 5 * 5 * 5 * 5 = 5⁴

y⁴ - 625 = y⁴ - 5⁴

= (y²)² - (5²)² {a = y² ; b = 5²}

= (y² + 5²)(y² - 5²)

= (y² + 25)(y² - 5²)

= (y² + 25)(y + 5)(y - 5)