Additional Mathematics – Quadratic functions | e-Consult

Divide by 2: x² − 4x + 3 ≥ 0 → (x − 1)(x − 3) ≥ 0. The product is non‑negative when x ≤ 1 or x ≥ 3. Hence the solution set is x ≤ 1 ∪ x ≥ 3, i.e. (‑∞, 1] ∪ [3, ∞).