Step-by-step explanation:
Equation of circle with (h,k) as center and radius r is given by,
(x-h)²+(y-k)² = r²
a) 3x²+3y²=75
Dividing by 3
x²+y²=25
(x-0)²+(y-0)² = 5²
Center (0,0) and radius 5
b) 2(x+1)²+2(y+2)²=10
Dividing by 2
(x+1)²+(y+2)²=5
(x-(-1))²+(y-(-2))²= 2.236²
Center (-1,-2) and radius 2.236
c) 4(x−2)²+4(y−9)²−64=0
4(x−2)²+4(y−9)²= 64
Dividing by 4
(x−2)²+(y−9)²= 16
(x−2)²+(y−9)²= 4²
Center (2,9) and radius 4
