Question

At what time would you reach 15ft above the water if you jump off a cliff using the formulaH(t)=-16t^2+8t+24

Answer 1

Answer:

  1.079 seconds

Step-by-step explanation:

You want to find t when H(t) = 15.

  15 = -16t^2 +8t +25

  10/16 = t^2 -1/2t . . . . . . subtract 24, divide by -16

  10/16 + 1/16 = t^2 -1/2t +(1/4)^2 . . . . . add (1/4)^2 to complete the square

  11/16 = (t -1/4)^2

  t -1/4 = √(11/16) . . . . . take the positive square root

  t = 1/4 +(√11)/4 = (1+√11)/4 . . . . use a common denominator

You would be 15 ft above the water at t = (1+√11)/4 ≈ 1.079 seconds.