Find the inflection points of f(t) = t^4 + t^3 − 9t^2 + 6

Find the inflection points of f(t) = t^4 + t^3 − 9t^2 + 6. Give exact answers.

t=??? (smaller value)
t=??? (large value)

f'(t) = 4t^3 + 3t^2 - 18t
f''(t) = 12t^2 + 6t - 18 = 6(2t^2 + t - 3) = 6(2t+3)(t-1)
Solve f''(t) = 0 for t,
t1 = -3/2
t2 = 1