SOLUTION: How do you solve this quadratic equation 2x^2+8x-1=0?

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Question 230806: How do you solve this quadratic equation 2x^2+8x-1=0?
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
The quadratic equation is one way, and it always works. Other methods work some of the time.
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 2x%5E2%2B8x%2B-1+=+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=%288%29%5E2-4%2A2%2A-1=72.

Discriminant d=72 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-8%2B-sqrt%28+72+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%288%29%2Bsqrt%28+72+%29%29%2F2%5C2+=+0.121320343559642
x%5B2%5D+=+%28-%288%29-sqrt%28+72+%29%29%2F2%5C2+=+-4.12132034355964

Quadratic expression 2x%5E2%2B8x%2B-1 can be factored:
2x%5E2%2B8x%2B-1+=+%28x-0.121320343559642%29%2A%28x--4.12132034355964%29
Again, the answer is: 0.121320343559642, -4.12132034355964. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+2%2Ax%5E2%2B8%2Ax%2B-1+%29