Strict positivity of four x to the fourth minus seven x plus four

Proved

WorkbookSource.base_5070

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

For all real $x$ prove that: $4x^4-7x+4>0$

Source: InternLM Lean-Workbook, record lean_workbook_5070 (Apache-2.0). Complete source proposition preserved; proof developed independently.

Preamble

import Mathlib
open Real Nat

Formal statement

theorem WorkbookSource.base_5070 (x : ℝ) : 4 * x^4 - 7 * x + 4 > 0  :=  by sorry

Source