(d) The point of intersection of the pair of lines f(x,y)≡x2+xy+2y2−3x+2y+4=0 is same as the intersection of curve obtaining after partial differentiating of the curve W.r.t. x and y respectively. ∵
∂f
∂x
=2x+y−3=0... (i) and
∂f
∂y
=x+4y+2=0... (ii) By cross-multiplication method, we get