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A football is kicked into the air from an initial height of 3 feet. the height, in feet, of the football above the ground is given by s(t)=-16t^2+35t+3.
Where t is time in seconds and t>=0. which is closest to the time when the football will be 20ft above the ground??

A) 2.72 seconds
B) 0.73 seconds or 1.46 seconds
C) 0.53 seconds
D) 0.53 seconds or 2.72 seconds

Respuesta :

carlosego
 For this case we have the following quadratic equation:
 [tex]s (t) = - 16t ^ 2 + 35t + 3 [/tex]
 Where,
 t: time
 s: height of the ball
 By the time the height is 20 feet we have:
 [tex]-16t ^ 2 + 35t + 3 = 20 [/tex]
 Rewriting the polynomial we have:
 [tex]-16t ^ 2 + 35t + 3-20 = 0 -16t ^ 2 + 35t-17 = 0[/tex]
 Using the quadratic formula we have:
 [tex]t = \frac{-b+/- \sqrt{b^2 - 4ac}}{2a} [/tex]
 Substituting values we have:
 [tex]t = \frac{-35+/- \sqrt{35^2 - 4(-16)(-17)}}{2(-16)} [/tex]
 Doing the calculations we have the roots are:
 [tex]t1 = 0.728 t2 = 1.46[/tex]
 Answer:
 the time when the football will be 20ft above the ground is:
 B) 0.73 seconds or 1.46 seconds
emilybrown0812

Answer:

B

Step-by-step explanation:

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