The equation of circle of radius r and center (h,k) is given by
[tex](x-h)^2 + (y-k)^2 = r^2[/tex]
And it is given that the center is origin and it passes through (2,3).
So values of h and k are 0 each and values of x and y are 2 and respectively .
Substituting these values in the equation, we will get
[tex](2-0)^2 + (3-0)^2 = r^2
\\
4+9 = r^2
\\
r^2 =13[/tex]
Substituting the values of h,k and r, we will get
[tex]x^2 + y^2 = 13[/tex]
