I am doing a deductive proof question, and am a bit stuck.
I've managed to do the first part, which was to prove that:
$\frac{x^2+y^2}{2}\ge xy$
I did this by starting with
$(x-y)^2\ge 0$
and rearranging
The second part wants me to use the first part, and prove that:
$x^2+y^2+z^2\ge xy + yz + zx$
I'm stuck, specifically because it says "using the first part, and 2 similar properties". What might these properties be? Is it referring to the property that squares are always greater than 0? Any hints would be really helpful please.