The parabola $y=x^2-8x+15$ cuts the x axis at P and Q. A circle is drawn through P and Q so that the origin is outside it. Find the length at a tangent to the circle from O.
My approach :
Since the parabola $y=x^2-8x+15$ cuts the x axis therefore, its y coordinate is zero,
Solving the equation: $x^2-8x+15=0$ we get two points $(3,0)$ and $(5,0)$.
Now how to proceed further with these two points, please suggest. thanks..