3-16 Find the limit, if it exists, or show that the limit does not exist. 3. lim (5x³- x2 y2) (x, y)-(1.2) 4. lim (x, y)-(1.-1) 5. lim exy cos(x + y) x² - 4y² (x, y)-(0.0) x² + 2y 2 y² sin²x 5y4 cos²x 6. lim (x, y)(0, 0) x + xy-y 7. lim 8. lim (xy)-(0,0) x + y (x, y)-(1, 0) (x-1)² + y² xy 9. lim x² sin² y 10. lim (x, y)-(0, 0) x² + y² (x,y)(0,0) x² + 2y² x²yey 11. lim 12. lim xy4 (x, y)-(0,0) x²+4y² (x, y)-(0, 0) x + y x² + y² 13. lim (x, y)-(0,0) x² + y²+1-1