Question: a circle has a center (3, 5) and the point (4, -3) on the circumference. 1. find the radius of the circle. 2. write an equation of the circle in standard form.

We know that
the equation of a circle in standard form is 
(x-h)²+(y-k)²=r²
where 
(h,K)> is the center> (3,5)

the radius is the distance between (3,5) and the point (4, -3) 

r=√[(-3-5)²+(4-3)²]> r=√65 units
radius r=√65

(x-h)²+(y-k)²=r²> (x-3)²+(y-5)²=√65²

(x-3)²+(y-5)²=65