Bonjour
1) (7x + 3)² = (7x)² - 2 × 7x × 3 + 3² = 49x² - 42x + 9
2) A = (3x + 5) ²
= (3x + 5) × (3x + 5)
= 3x × 3x + 3x × 5 + 5 × 3x + 5 × 5
= 9x² + 3x × 5 + 5 × 3x + 5 × 5
= 9x² + 15x + 5 × 3x + 5 × 5
= 9x² + 15x + 15x + 5 × 5
= 9x² + 15x + 15x + 25
= 9x² + 30x + 25
Solution : A = 9x² + 30x + 25
B = (6 + 4x) ²
= (6 + 4x) × (6 + 4x)
= 6 × 6 + 6 × 4x + 4x × 6 + 4x × 4x
= 36 + 6 × 4x + 4x × 6 + 4x × 4x
= 36 + 24x + 4x × 6 + 4x × 4x
= 36 + 24x + 24x + 4x × 4x
= 36 + 24x + 24x + 16x²
= 36 + 48x + 16x²
= 16x² + 48x + 36
Solution : B = 16x² + 48x + 36
C = (8y - 3)²
= (8y - 3) × (8y - 3)
= 8y × 8y - 8y × 3 - 3 × 8y - 3 × (-3)
= 64y²- 8y × 3 - 3 × 8y - 3 × (-3)
= 64y²- 24y - 3 × 8y - 3 × (-3)
= 64y²- 24y - 24y - 3 × (-3)
= 64y²- 24y - 24y + 9
= 64y²- 48y + 9
Solution : C = 64y²- 48y + 9
D = (10 - 7y)²
= (10 - 7y) × (10 - 7y)
= 10 × 10 - 10 × 7y - 7y × 10 - 7y × (-7y)
= 100 - 10 × 7y - 7y × 10 - 7y × (-7y)
= 100 - 70y - 7y × 10 - 7y × (-7y)
= 100 - 70y - 70y - 7y × (-7y)
= 100 - 70y - 70y + 7y × 7y
= 100 - 70y - 70y + 49y²
= 100 - 140y + 49y²
= 49y ² - 140y + 100
Solution : D = 49y ² - 140y + 100
