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?

9514 1404 393

  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.

c. 27 units.

step-by-step explanation:

we are told that in circle a, ∠bae ≅ ∠dae.

we can see from our given diagram that in and ;

, as these are radii of our given circle.

therefore, by sas congruence postulate.

hence, side be will be equal to side de as corresponding parts of congruent triangles are congruent. so we can set an equation to find the value of x as:

now let us substitute x=17 in the expression for the length of be.

therefore, length of be will be 27 units and option c is the correct choice.