A natural number is less than the sum of its opposite and 8. find all such numbers​

Anyone know? will mark brainliest if you're correct!

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 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)

What is the distance from zero if a quadratic function has a line of symmetry at x=-3 and a zero at 4