Jensen gap for f=x²: (x₁−x₂)²/4 symbolic; (1,3) pin = 1; diag = 0

Exact sympy witness that x ↦ x² is strictly convex: the two-point Jensen gap (f(x₁) + f(x₂))/2 − f((x₁ + x₂)/2) factors as (x₁ − x₂)²/4 symbolically, which sp.factor returns identically in the two real symbols x₁, x₂. Concrete pin: at…