Let S(x,y)=x2+y2+x−y−2
A) S(−2,1)=4+1−2−1−2=0⇒ hence (−2,1) lies on circle
B) S(2,−1)=4++2+1−2>0⇒ hence (2,−1) lies outside circle
C) S(0,1)=0+1+0−1−2<0⇒ hence (0,1) lies inside circle
D) S(2.3)=4+9+2−3−2>0 hence (2.3) lies outside circle
And tangent at (1,0) is 3x−y−3=0 which passes through (2,3)