SOLUTION: Find the x-intercept. y=x^2+4x-1 I am stuck on this..please help!

Question 211828This question is from textbook Introductory Algebra
: Find the x-intercept.
y=x^2+4x-1
I am stuck on this..please help! This question is from textbook Introductory Algebra

Answer by drj(1380) (Show Source): You can put this solution on YOUR website!
Find the x-intercept.
y=x^2+4x-1
I am stuck on this..please help!

Step 1. The x-intercept occurs when y=0. So let's set y=0=x^2+4x-1.

Step 2. Now use the quadratic formula given as:

where a=1 b=4 and c=-1

Step 3. Substitute above values in quadratic formula and you get the following. Note the values of x where y=0 and observe them on the graph.

Also, note a quadratic equation is basically a parabola if the value of x are real numbers.

Solved by pluggable solver: SOLVE quadratic equation with variable

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:

If you have any questions, I have a video also on the quadratic equation and you can contact Dr J at john@e-liteworks.com or visit my website at http://www.FreedomUniversity.TV for more step-by-step videos in math.
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