google is your friend:
https://math.stackexchange.com/questions/1967491/suppose-we-have-the-following-identity-px-1-py2-ax2-bxy-cy2-f
Suppose we have the following identity:
(px + (1-p)y)^2 = Ax^2 + Bxy + Cy^2.
Find the minimum of max(A,B,C) over 0 \leq p \leq 1.
2 answers
but it has no response