Please Can anyone help me with these?

Question 6 (10 points) ✓ saved what is the center of a circle described by the equation x2 + y2 +10y = -16? . (0,-5) (0,5) (-5,0) (5,0)

The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)