Solve for x. help please

Find parametric equations for the line. (enter your answers as a comma-separated list of equations. let x, y, and z be functions of t.) the line in the direction of the vector 5 i + 5 j − 6k and through the point (−4, 4, −2).

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)

Acircle has a circumference of 7.850 units. what is its radius?