We take the equation <span>d = -16t^2+12t</span> and subtract d from both sides to get 0<span> = -16t^2+12t - d We apply the quadratic formula to solve for t. With a = -16, b = 12, c = -d, we have t = [ -(12) </span><span>± √( 12^2 - 4(-16)(-d) ) ] / [2 * -16]</span> = [- 12 ± √(144-64d) ] / (-32) = [- 12 ± √16(9-4d)] / (-32) = [- 12 ± 4√(9-4d)] / (-32) = 3/8 ±√(9-4d) / 8 The answer to your question is t = 3/8 ±√(9-4d) / 8
