algebra

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a model rocket is shot straight up from a roof the height at any time t is aproximated by the model h=-t(squared) +3t+28,where h is the height in metres and t is the time in seconds . When does the rocket hit the ground?

  • algebra -

    hit the ground? then h=0

    0=-t^2 + 3t+28=t^2-3t-28=(t-7)(t+4)=0

    t=7 seconds

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