For the function f(x,y)=(2x^2+3y^2+8)/(4x^2-9y^2).
a) Enter the coordinates of a point in the domain of f(x,y).
b) Enter the coordinates of a point not in the domain of f(x,y),with positive x-value.
c) Enter the coordinates of a point not in the domain of f(x,y)with negative x-value.