I am really stuck on this question...
I have my Maths Prelim in a couple of days and I think I am ok with most things however I am stumped by this one question.
The line y-2x=k is tangent to the circle x^2+y^2-2x-4=0, where k>0.
Find the value of k.
I have got to x^2+(k-2x)^2-2x-4=0, I know that I need to apply that to the discriminant (b^2-4ac) but I don't know how to get that into the discriminant.
Thanks For Any help,