403(1): デフォルトの名無しさん [sage] 2024/04/17(水) 10:48:26.99 ID:QYenzWQY(1/2) AAS
In 1888, Hilbert showed that every non-negative homogeneous polynomial in n variables and degree 2d can be represented as sum of squares of other polynomials if and only if either (a) n = 2 or (b) 2d = 2 or (c) n = 3 and 2d = 4.