SOLUTION: Quadratic equation parabola.. y=16-x-x^2

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Question 982205: Quadratic equation parabola..
y=16-x-x^2
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
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y=-x^2-x+16
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case -1x%5E2%2B-1x%2B16+=+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=%28-1%29%5E2-4%2A-1%2A16=65.

Discriminant d=65 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--1%2B-sqrt%28+65+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-1%29%2Bsqrt%28+65+%29%29%2F2%5C-1+=+-4.53112887414927
x%5B2%5D+=+%28-%28-1%29-sqrt%28+65+%29%29%2F2%5C-1+=+3.53112887414927

Quadratic expression -1x%5E2%2B-1x%2B16 can be factored:
-1x%5E2%2B-1x%2B16+=+-1%28x--4.53112887414927%29%2A%28x-3.53112887414927%29
Again, the answer is: -4.53112887414927, 3.53112887414927. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+-1%2Ax%5E2%2B-1%2Ax%2B16+%29

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