If x, y and z are real numbers such that: x + y + z = 5 and xy + yz + zx = 3, what is the largest value that x can have ?

x + y + z = 5

x^2 + y^2 + z^2 + 2xy + 2yz + 2zx = 25

2xy + 2yz + 2zx = 6

x^2 + y^2 + z^2 = 19

x max = √19

sorry, something wrong.

*Edited on ***November 18, 2003, 7:54 am**