Answer:
Step-by-step explanation:
The equation is a parabola, that opens up downwards, and the point from which Sarah throws the ball is 5 feet off the ground. so set the height to zero ( when the ball reaches the ground ) and solve for t
0 = -16 + 18t + 5
use quadratic equation :)
-b +- sqrt( - 4ac) / 2a
-18 +- sqrt[ - 4 (-16)(5) ] / 2(-16)
-18 +- sqrt[324 +320 ] / -32
-18 +- sqrt[644] / -32
-18 +- 25.377155 / -32
do the positive choice :
-18 + 25.377155 / -32
7.377155 / -32
-0.2305 ( so this answer would be where the ball would hit the ground if the arc extended down to the ground behind where Sarah throws the ball from. so this answer doesn't count in our domain. Because it's before Sarah throws the ball)
do the negative choice:
-18 - 25.377155 / -32
1.355536 ( this answer looks good, about 1.35 seconds for the ball to fly , this was more of a toss than a throw. )
t = 1.4 seconds ( rounded to nearest 10th )