My Math Forum how to find When does Delbert's book pass him on its way down?

 Algebra Pre-Algebra and Basic Algebra Math Forum

May 11th, 2017, 04:24 PM   #1
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Joined: Feb 2016
From: seattle

Posts: 377
Thanks: 10

how to find When does Delbert's book pass him on its way down?

Hi I know it says to use a calculator but I am hoping and guessing it's not to hard to find this answer or help me find it.

Thanks!
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 May 11th, 2017, 05:41 PM #2 Math Team   Joined: Jul 2011 From: Texas Posts: 2,738 Thanks: 1388 $h=-16t^2+20t+300$ Time it reaches the highest point is at the vertex ... $t=\dfrac{-b}{2a}=\dfrac{-20}{2(-16)}=\dfrac{5}{8} \, sec$ $h\left(\dfrac{5}{8}\right)=-16\left(\dfrac{5}{8}\right)^2+20\left(\dfrac{5}{8} \right)+300=-\dfrac{25}{4}+\dfrac{25}{2}+300 = 306.25 \, ft$ Passes the starting point on the way down ... $300=-16t^2+20t+300$ $0=-4t(4t-5) \implies t=\dfrac{5}{4} \, sec$ Thanks from GIjoefan1976
 May 15th, 2017, 01:01 PM #3 Senior Member   Joined: Feb 2016 From: seattle Posts: 377 Thanks: 10 Thanks as always skeeter!

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