Question 1031237
How would the discriminant be zero?

{{{(x-r)^2=0}}}

How many zeros?




{{{(x-r)^2=0}}}
{{{x^2-2rx+r^2=0}}}


{{{x=(2r+- sqrt((-2r)^2-4*1*r^2))/2}}}

Within that solution is the discriminant, {{{sqrt(4r^2-4r^2)=0}}}, which came from starting the equation as perfect square equated to zero.  The equation has EXACTLY ONE solution.