Newton-Raphson's method is applied to solve the equations
f (x,y) = -8xy² + 9 y³ + 8x² + 4xy + 7y² - 50x + 56
g (x,y) = -6x³ -6x²y - 9y³ -9x² -4y² -192y +313

Determine the expression for the Jacobian matrix