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Math Help - looks easy but stuck on one step

  1. #1
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    looks easy but stuck on one step

    Not going to write out the whole question but here's the basics:

    h = -0.5t^2g + d

    h = height
    t = time
    g = gravity
    d = starting height (which is 100m)

    Find how long it takes a rock to fall to a height of 25m on each planet.
    gravity for mars is g = 3.7m/s^2, gravity for venus is g = 8.9m/s^2

    so I've got 25 = -0.5t^2(3.7) + 100

    and that's as far as I can get lol, all the previous questions have been in the form of y = ax^2 + bx + c, and I'm find with those, I'm just not sure what to do when there's multiplication. Can I multiply a number by a squared number? Do I do something to the squared number first? Maybe just multiply it by -0.5t to get t (bx)?
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  2. #2
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    Quote Originally Posted by vicereine View Post
    Not going to write out the whole question but here's the basics:

    h = -0.5t^2g + d

    h = height
    t = time
    g = gravity
    d = starting height (which is 100m)

    Find how long it takes a rock to fall to a height of 25m on each planet.
    gravity for mars is g = 3.7m/s^2, gravity for venus is g = 8.9m/s^2

    so I've got 25 = -0.5t^2(3.7) + 100

    and that's as far as I can get lol, all the previous questions have been in the form of y = ax^2 + bx + c, and I'm find with those, I'm just not sure what to do when there's multiplication. Can I multiply a number by a squared number? Do I do something to the squared number first? Maybe just multiply it by -0.5t to get t (bx)?
    25 = -0.5t^2(3.7) + 100

    => -75 = -0.5t^2(3.7)

    => 150 = t^2(3.7)

    => 150/(3.7) = t^2

    Now square root both sides.
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