Question 211828
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:


{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 


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.



*[invoke quadratic "x", 1, 4, -1]


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.