In: Advanced Math
(12%) For the following 4 functions, check if you can calculate a constant c so that the function is a PDF over the whole plane or state that such c does not exist and the corresponding function is not a PDF (state the reason for that). Note the signs of the coefficients of x2 and y2 are all different). You do not have to calculate the constant c; just provide reasoning for if that exists or not.
f(x, y) = c e^(-x^2+xy-y^2 )
g(x, y) = c e^(-x^2+xy+y^2 )
h(x, y) = c e^(x^2+xy-y^2 )
k(x, y) = c e^(x^2+xy+y^2 )
f(x, y) = c e^(-x^2+xy-2y^2 )
g(x, y) = c e^(-x^2+xy+〖2y〗^2 )
h(x, y) = c e^(x^2+xy-2y^2 )
k(x, y) = c e^(x^2+xy+〖2y〗^2 )