Bonsoir ,
1. (4x+7)²
= (4x)² + 7² + 2 × 4x × 7
= 16x² + 49 + 98x
2. (6+2y)² - (6-2y)²
= 6² + (2y)² + 2 × 6 × 2y - ( 6² + (2y)² - 2 × 6 × 2y )
= 36 + 4y² + 24y - ( 36 + 4y² - 24y )
= 36 + 4y² + 24y - 36 - 4y² + 24y
= 48y
3. (x+3)² - (x+3) (x-3)
= x² + 3² + 2 × x × 3 - ( x² - 3² )
= x² + 9 + 6x - ( x² - 9 )
= x² + 9 + 6y - x² + 9
= 6y + 18 .