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Thread: Factoring using the destributive property-Word Problem?

  1. #1
    Mar 2008

    Question Factoring using the destributive property-Word Problem?

    Our algebra I class is working on factoring using the distributive property. And there is a word problem on homework that I simply don't even no where to start. Here it is:

    Miss Moore's science class launched a rocket at ground level with in an initial upward velocity of 60 feet per second. The height h of the rocket in feet above the ground after t seconds is modeled by the equation h=60t-16t^2. How long was the rocket in the air before it returned to the ground?
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  2. #2
    Senior Member topher0805's Avatar
    Jan 2008
    Notice that the path traveled by the rocket will model that of a parabola. Also notice that when the rocket reaches the ground, the height will be 0.

    So, we set our expression for Height equal to 0:

    $\displaystyle 60t-16t^2 = 0$

    Now rearrange so that it is in quadratic form:

    $\displaystyle -16t^2+60t+0 = 0$

    Now solve for t. Remember that you will get two values, since it is a quadratic. One of these roots will be 0, because at time 0, the rocket is still on the ground and therefore has a height of 0.

    The second root will tell you the total time that the rocket was in the air.
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