Question 204457
Calculate the value of the discriminant of x2+4x+4=0
By examining the sign of the discriminant in part a, how many x-intercepts would the graph of x2+4x+4=0 have? Why? 
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The discriminant is b^2 - 4ac, which in this case is zero (0).  That means there is one x-intercept - the x-axis is tangent to the curve at its vertex.
This is covered well by the onsite solver, too.
*[invoke solve_quadratic_equation 1,4,4]