Bonsoir,
• (a+b)² = a² + 2ab + b
Exemples :
(2x + 3)² (forme factorisée)
= (2x)² + 2
= 4x² + 12x + 9 (forme développée)
x² + 4x + 4
= (x×x) + 2*x×2 + 2²
= (x+2)²
• (a–b)² = a² – 2ab + b²
Exemples :
(3–2x)²
= 3² – 2×3×2x + (2x)²
= 9 – 12x + 4x²
25x² – 20x + 4
= (5x)² – 2 × 5x × 2 + 2²
= (5x–2)
• a² – b² = (a – b)(a + b)
Exemples :
16x² – 25
= (4x)² – 5²
= (4x – 5)(4x + 5)
(3 – 2x)(3 + 2x)
= 3² – (2x)²