SOLUTION: x2+7x=18

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Question 615100: x2+7x=18
Answer by asuar010(338) About Me  (Show Source):
You can put this solution on YOUR website!
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B7x%2B-18+=+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=%287%29%5E2-4%2A1%2A-18=121.

Discriminant d=121 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-7%2B-sqrt%28+121+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%287%29%2Bsqrt%28+121+%29%29%2F2%5C1+=+2
x%5B2%5D+=+%28-%287%29-sqrt%28+121+%29%29%2F2%5C1+=+-9

Quadratic expression 1x%5E2%2B7x%2B-18 can be factored:
1x%5E2%2B7x%2B-18+=+1%28x-2%29%2A%28x--9%29
Again, the answer is: 2, -9. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B7%2Ax%2B-18+%29