Stephanie is a very good soccer player. She can kick a soccer ball with an initial velocity of 21.3m/sec. The function that represents the height of the ball with respect to time is h(x) = -4.9x^2 + 21.3x. About how many seconds will it take for the ball to hit the ground.

Answer 1

when it hits the ground, h = 0
0 = -4.9x^2 + 21.3x
4.9x^2 - 21.3x = 0
x(4.9x - 21.3) = 0
x = 0 , which corresponds to the moment she kicks the ball
or
x = 21.3/4.9 = appr 4.4 seconds