14.6)

1. 2xy^3 3x^2y^2 4z^3 | 2s t^2 2st | 7s^6t^6+8s^7t^4

3. 6rs^2 | 2s^3+4r^3

5. -10sin(10u-20v) 20sin(10u-20v)

7. xe^x^2+xy

15. 2cos2

27. -(2xy+z^2)/(2xz+y^2)

29.-(xe^xy+1)/(xcos(xz))

31. -1/2


14.7)

1. 0,0-->pos neg (2sqrt(2),sqrt(2)) min value=-4

3. 0,0-->(13/64,-13/32) and (-1/4,,1/2)

5.0,0 1,0 0,-1 1/3,-1/3

7. -2/3,-1/3

13. 0,0 1,1 -1,-1

19. 1,1/2

21.3/2,-1/2

23.-1/6,-17/18

29. max=2 min=0

35. 1/3