SOLUTION: a stone is thrown vertically upwards at a speed of 24 m/s. its height h meters after t seconds is given approximately by the formula h=24t-5t squared. Use this formula to find when

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Question 281579: a stone is thrown vertically upwards at a speed of 24 m/s. its height h meters after t seconds is given approximately by the formula h=24t-5t squared. Use this formula to find when the stone is 27 meters up, and explain the double answer.

apply thr quadratic formula
could someone please help?
Found 2 solutions by solver91311, Alan3354:
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


The solution to the general quadratic equation, is the quadratic formula:



For your equation, , , and , so:



The discriminant, that is the portion of the formula under the radical, can readily be seen to be less than zero. That means that the roots are a conjugate pair of complex numbers:



John

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
x^2 - 3x + 7 = 0
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These are all the same:
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Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B-3x%2B7+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%28-3%29%5E2-4%2A1%2A7=-19.

The discriminant -19 is less than zero. That means that there are no solutions among real numbers.

If you are a student of advanced school algebra and are aware about imaginary numbers, read on.


In the field of imaginary numbers, the square root of -19 is + or - sqrt%28+19%29+=+4.35889894354067.

The solution is , or
Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B-3%2Ax%2B7+%29