SOLUTION: Please help me solve this problem below. An object is launched into the air from a ledge 6 feet off the ground at initial vertical velocity of 96 feet per second. Its height H,

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Please help me solve this problem below. An object is launched into the air from a ledge 6 feet off the ground at initial vertical velocity of 96 feet per second. Its height H,       Log On


   



Question 1090948: Please help me solve this problem below.
An object is launched into the air from a ledge 6 feet off the ground at initial vertical velocity of 96 feet per second. Its height H, in feet, at t second is given by the equation H = 16t^2+96t+16. Find all the times t that the object is at a height of 160 feet off the ground.

Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.
First you need to learn THIS:

    When you consider the problems like this one, the correct form of the equation for the height is 

    H(t) = -16t^2 + 96t + 16.


    Notice the sign "-" (minus) at the quadratic term.

    Your writing in the post was incorrect.


Second, all you need to do is to solve the equation H(t) = 0, or, which is the same,

-16t%5E2+%2B+96t+%2B+16 = 0.

For it, divide both sides by 16. You will get

-t^2 + 6t + 1 = 0,    or, which is simpler (and equivalent !)

t^2 -6t -1 = 0.


t%5B1%2C2%5D = %286+%2B-+sqrt%286%5E2+-4%2A%28-1%29%29%29%2F2 = %286+%2B-+sqrt%2840%29%29%2F2 = 3+%2B-+sqrt%2810%29.


Only positive root makes sense.


Answer.  t = 3+%2B+sqrt%2810%29 seconds.

Solved.