A cyclic mixed cubic ratio bounds a normalized quadratic sum
ProvedWorkbookSource.base_12418lean-workbooksource-checked
Prove that for all positive real numbers and , \sum_{cyc} (a-b)^2(\frac{c}{a}-\frac{2}{a+b+c}) \geq 0$ But I don't know how to continue
Source: InternLM Lean-Workbook, record lean_workbook_12418 (Apache-2.0). Complete source proposition preserved; proof developed independently.
Preamble
import Mathlib open Real Nat
Formal statement
theorem WorkbookSource.base_12418 (a b c : ℝ) (ha : 0 < a) (hb : 0 < b) (hc : 0 < c) : (a * b ^ 2 / c ^ 2 + b * c ^ 2 / a ^ 2 + c * a ^ 2 / b ^ 2 + a + b + c) ≥ 6 * (a ^ 2 + b ^ 2 + c ^ 2) / (a + b + c) := by sorry
Source