Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Completing The Square

  1. Jan 31, 2005 #1
    I dont think this is corrent...

    Question By completiing the square determine the maximum height of the ball and how long it takes to reach the maximum height

    h=-5t^2+30t+1.5

    Work:
    =t^2-6t+1.5/5
    (t^2-6t+9)1.5/-5 + 9
    (t-3)^2+43.5/5
    That would mean the time of the ball to get to the max height is 3 seconds but when I graph it I get 6 seconds?
     
  2. jcsd
  3. Jan 31, 2005 #2

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    You've completed the square for another function... :confused: Not for the one you initially posted...Where did you put that "-5" you factored.??

    Daniel.
     
  4. Jan 31, 2005 #3

    HallsofIvy

    User Avatar
    Science Advisor

    that should be h/5= (t^2- 6t+9)- 1.5/5+ 9

    What is h when t= 6?
    h(6)= -5(36)+ 30(6)+ 1.5= -31+ 30+ 1.5= -1+ 1.5= 0.5 m. I hardly think that is the maximum height!
    What exactly did you graph?

    When I graph h= -5t2+ 30t+ 1.5, I get the maximum (h=46.5) at t= 3.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook