quadratic equations

Question

An object is dropped from a window. The height S of the object after t seconds is given by the equation S= -16 t squared+ 100. Find how many seconds pass before the object hits the ground. (Hint: The object is on the ground when S = 0.)

Answer 1

S = -16t² + 100

0 = -16² + 100

-100 = -16t²

100/16 = t^t

±10/4 = t