2 2 s - k + 18*s + 81
s^2 - k^2 + 18*s + 81
1*(k + 9 + s)*(k + -9 - s)
(1*(k + (9 + s)))*(k - (9 - s))
81.0 + s^2 - k^2 + 18.0*s
(9 + k + s)*(9 + s - k)