Question

How do you factor 9y^4- 1

Answer 1

Recognize the difference of 2 perfect squares

remember
a²-b²=(a+b)(a-b)


9y⁴=(3y²)²
1=1²

9y⁴-1=(3y²)²-(1)²=(3y²+1)(3y²-1)
if we wanted to force a factor again
(3y²+1)(y√3+1)(y√3-1)