# Math Help - Proof: X+y+z=1 Then XY +XZ+YZ =1/2

1. ## Proof: X+y+z=1 Then XY +XZ+YZ =1/2

We never went over this in class, and am trying to get this as a bonus question

x+y+z=1
Then X*Y + X*Z + Y*Z < or = 1/2

I can show examples but that will take forever. There has to be a general way to show this.

2. Originally Posted by probowl8885
We never went over this in class, and am trying to get this as a bonus question

x+y+z=1
Then X*Y + X*Z + Y*Z < or = 1/2

I can show examples but that will take forever. There has to be a general way to show this.