1) > 1
2) < 1
3) > 0
4) < 0
Solution: (2) < 1
Since AM > GM
[a2 + x2] / 2 > √a2x2 [a2 + x2] > 2ax [b2 + y2] > 2by [c2 + z2] > 2cza2 + x2 + b2 + y2 + c2 + z2 > 2 (ax + by + cz)
(a2 + b2 + c2) + (x2 + y2 + z2) > 2 (ax + by + cz)
1 + 1 > 2 [ax + by + cz] [ax + by + cz] < 1