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0
77
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a. An arrow is shot upward from a height of 5 feet with an initial velocity of 128 feet per second. Its height, in feet, t seconds after being released is modeled by -16t2+128t+5. To the nearest tenth of a second, how many seconds after release will the arrow first be 150 above the ground? 

 

b. A convex polygon with n sides has n(n-3)2diagonals. How many sides does a convex polygon with 14 diagonals have?

 

can you also show some work too? if you want :D 

 Aug 15, 2020
edited by Guest  Aug 15, 2020
 #1
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a. The arrow is at 150 feet at t = 8.

 

b. The number of diagonals is 14*(14 - 3)*2 = 308.

 Aug 15, 2020
 #2
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For a, you need to make the inequality 5+(-16t^2+128t+5)>150 and solve that. for b) just plug it in it's 14*11/2=77.

 

the guest answer is entirely wrong because the math expressions in the problem aren't as they should be, but i think i interpreted it right. nevertheless otherwise the guest did it right based on what the question said so dont be too hard on him/her.

 

Hope this helped!

 

laugh

 Aug 15, 2020
 #3
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150 = -16t^2 + 128t + 5

0 = -16t^2 + 128t - 145      Quadratic formula reveals t =~ 1.4 seconds

 

(is the arrow is travelling at 128 f/s initially....obviously 8 seconds is an incorrect answer)

 Aug 15, 2020

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