SOLUTION: I need help with this problem of finding the x intercepts. y = x^2 + 4x -1

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Question 173144: I need help with this problem of finding the x intercepts.
y = x^2 + 4x -1
Found 2 solutions by Alan3354, stanbon:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
I need help with this problem of finding the x intercepts.
y = x^2 + 4x -1
-----------------
At the x-intercepts, y is zero.
y = x^2 + 4x -1 = 0
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation (in our case ) has the following solutons:



For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=20 is greater than zero. That means that there are two solutions: .




Quadratic expression can be factored:

Again, the answer is: 0.23606797749979, -4.23606797749979. Here's your graph:
Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
finding the x intercepts.
y = x^2 + 4x -1
x^2 + 4x -1 = 0
x = [-4 +- sqrt(16 - 4*1*-1)]/2
x = [-4 +- sqrt(20)]/2
x = [-4 +-2sqrt(5)]/2
x = [-2 +-sqrt(5)]
=================================
Cheers,
Stan H.
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