Which equation is a linear function? hurry plz

How do i work this problem out using the equation a=pe^rt

Aball is thrown from a height of 139 feet with an initial downward velocity of 15 ft/s. the ball's height h (in feet) after t seconds is given by the following. h=139-15t-16t^2 how long after the ball is thrown does it hit the ground? round your answer(s) to the nearest hundredth. (if there is more than one answer, use the "or" button.) t =

The perimeter of a rectangle is 42 inches. if the width of the rectangle is 6 inches, what is the length