SOLUTION: How do I use this formula x=(-bą√(b^2-4ac))/2a and find out what a, b, and c are, then plug those numbers in and get x-intercepts? The equation to solve is y=x^2+4x-1

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: How do I use this formula x=(-bą√(b^2-4ac))/2a and find out what a, b, and c are, then plug those numbers in and get x-intercepts? The equation to solve is y=x^2+4x-1      Log On


   

Question 247661: How do I use this formula x=(-bą√(b^2-4ac))/2a and find out what a, b, and c are, then plug those numbers in and get x-intercepts? The equation to solve is
y=x^2+4x-1
Answer by oberobic(2304) 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%2B4x%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=%284%29%5E2-4%2A1%2A-1=20.

Discriminant d=20 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-4%2B-sqrt%28+20+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%284%29%2Bsqrt%28+20+%29%29%2F2%5C1+=+0.23606797749979
x%5B2%5D+=+%28-%284%29-sqrt%28+20+%29%29%2F2%5C1+=+-4.23606797749979

Quadratic expression 1x%5E2%2B4x%2B-1 can be factored:
1x%5E2%2B4x%2B-1+=+1%28x-0.23606797749979%29%2A%28x--4.23606797749979%29
Again, the answer is: 0.23606797749979, -4.23606797749979. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B4%2Ax%2B-1+%29