Write an equation for a circle given that the endpoints of the diameter are
(-8,5) and (4,-3)

(2,2)

so Using the distance formula,

d = sqrt(x2-x1)^2 +(y2-y1)^2 .

Substituting the values of x and y.

we get,

d = sqrt(-4-8)^2 +(-3-7)^2

d = 2 sqrt 61  

diameter = 2*radius

              = 2 sqrt 61

              = 2 r

              = r

              = sqrt 61

          r^2 = 61  

midpoint of the diameter is:  

Xm= 8-4 / 2

     = 2  

Ym = 7-3 / 2  

     = 2  

Hence,

The center is (2,2)  

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so: