Question

A model rocket fired from the ground at time t can be modeled by the equation h= -490t² + 1120t. When is the height of the model rocket 640 centimeters?

Answer 1

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Answer:

  t = 1 1/7 ≈ 1.1429 seconds

Step-by-step explanation:

Filling in the given height, we can solve for t:

  640 = -490t^2 +1120t

  49t^2 -112t +64 = 0 . . . . . divide by 10, put in standard form

  (7t -8)^2 = 0

  t = 8/7 . . . . . . . the value of t that makes the factor(s) zero

The model rocket will reach its maximum height of 640 cm after 1 1/7 seconds.