the equation of a circle with center (h,k) and radius r is
(x-h)²+(y-k)²=r²
so
given center is (3,-4)
(x-3)²+(y-(-4))²=r²
(x-3)²+(y+4)²=r²
find r² by subsitutiong the point taht it passes through which is (6,5)
so
(6-3)²+(5+4)²=r²
3²+9²=r²
9+81=r²
90=r²
so
(x-3)²+(y+4)²=90 is da equation
4th equation
