I'm trying to factor this and I just can't figure it out. Help?
r^4 s^4 - 81
2 answers
difference of two squares
r^4 s^4 - 81
(r^2s^2 - 9 )(r^2s^2 + 9 )
(rs-3)(rs+3)(r^2s^2+9)
(r^2s^2 - 9 )(r^2s^2 + 9 )
(rs-3)(rs+3)(r^2s^2+9)