SOLUTION: A ball is thrown upward with a velociity of 80ft/s from a height of 576ft. H= -16t^2+80t=576 gives the height,h, after t sec. Find the time when the ball is 300ft above the groun

Question 605863: A ball is thrown upward with a velociity of 80ft/s from a height of 576ft. H= -16t^2+80t=576 gives the height,h, after t sec. Find the time when the ball is 300ft above the ground. H value is 300

OK--I know how that I have to set it to zero by subtracting 300 from 576. It will not factor out evenly. After setting it up with the quadratic formula, I am still getting it wrong. Please help me. I am on my 5th problem like this and am severly struggleing.
Found 2 solutions by jim_thompson5910, Alan3354:
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Now use the quadratic formula to solve

or

or

or <--- Exact Solutions

or <--- Approximate Solutions

We now ignore the negative solution since a negative time value doesn't make any sense.

So the ball is 300 ft above the ground at approximately 7.34767985741632 seconds
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A ball is thrown upward with a velociity of 80ft/s from a height of 576ft. H= -16t^2+80t=576 gives the height,h, after t sec. Find the time when the ball is 300ft above the ground.
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It's H= -16t^2+80t + 576
H = 300
-16t^2+80t + 576 = 300
-16t^2+80t + 276 = 0

Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

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=24064 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: -2.34767985741633, 7.34767985741633. Here's your graph:

==============
t =~ 7.348 seconds
Ignore the negative time.
Ignore the "It can be factored." statement, too.

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