SOLUTION: An angry construction worker thros his wrench downward from a height of 128 feet with an initial vleocity of 32 feet per second, The height of the wrench above the ground after "t

Question 416300: An angry construction worker thros his wrench downward from a height of 128 feet with an initial vleocity of 32 feet per second, The height of the wrench above the ground after "t" seconds is given by:
S(t) = -16r^2 -32t +128
(a) what is the height of the wrench afer 1 second? (this one I got. It's 80 feet)
WHAT I DON"T GET IS:
(b) How long does tit take for the wrench to reach the ground?
I'm guessing something along the line of: 0=-16t^2-32=128
t^2+2t-9=0
THEN I GET STUCK,,,, PLEASE HELP!!! THANKS
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
t^2+2t-9=0
Since you can't factor, you must resort to the "quadratic formula".
Doing so yields:
t = {2.162, -4.162}
You can throw out the negative solution leaving:
t = 2.12 seconds
.
Details of quadratic follows:
.

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=40 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 2.16227766016838, -4.16227766016838. Here's your graph:

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