Please help with this problem

An arrow is shot vertically upward at a rate of 180ft/s. use the projectile formula h=−16t2+v0t to determine at what time(s), in seconds, the arrow is at a height of 420ft. round your answer(s) to the nearest tenth of a second.

The measures of the legs of a right triangle are 15m and 20m . what is the length of the hypotenuse

Find the condition that the zeros of the polynomial f(x) = x^3+3px^2+3px+r may be in a.p.