SOLUTION: A company has determined that the profit, in dollars, it can expect from the manufacture and sale of x tennis racquets is given by: P= -0.01x2 + 168x - 120,000. How many racquets s

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Question 180243: A company has determined that the profit, in dollars, it can expect from the manufacture and sale of x tennis racquets is given by: P= -0.01x2 + 168x - 120,000. How many racquets should the company manufacture and sell to earn a profit of $518,000?
Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
A company has determined that the profit, in dollars, it can expect from the manufacture and sale of x tennis racquets is given by: P= -0.01x2 + 168x - 120,000. How many racquets should the company manufacture and sell to earn a profit of $518,000
:
518000=-.01x^2+168x-120000
:
.01x%5E2-168x%2B638000
:
x=11000 and 5800
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case .01x%5E2%2B-168x%2B638000+=+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=%28-168%29%5E2-4%2A.01%2A638000=2704.

Discriminant d=2704 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--168%2B-sqrt%28+2704+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-168%29%2Bsqrt%28+2704+%29%29%2F2%5C.01+=+11000
x%5B2%5D+=+%28-%28-168%29-sqrt%28+2704+%29%29%2F2%5C.01+=+5800

Quadratic expression .01x%5E2%2B-168x%2B638000 can be factored:
.01x%5E2%2B-168x%2B638000+=+%28x-11000%29%2A%28x-5800%29
Again, the answer is: 11000, 5800. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+.01%2Ax%5E2%2B-168%2Ax%2B638000+%29