Bonjour,
Exercice 3 :
X ≥ 4
1)
Aire du rectangle BCEF :
[tex]A_{ABCD}[/tex] = (2x – 3)²
[tex]A_{AFED}[/tex] = (x + 1)(2x –
3)
[tex]A_{BCEF} = A_{ABCD} - A_{AFED}[/tex]
[tex]A_{BCEF} = (2x – 3)² -
(2x – 3)(x + 1)
2)
Développer et réduire A :
A = 4x² - 12x + 9 – (2x² + 2x –
3x – 3)
A = 4x² - 12x + 9 – 2x² + x + 3
A = 2x² - 11x + 12
3)
Factoriser A :
A = (2x – 3)² - (2x –
3)(x + 1)
A = (2x – 3)(2x – 3 – x – 1)
A = (2x – 3)(x – 4)
4)
Aire du rectangle BCEF pour x = 5
A = (2 * 5 – 3)(5 – 4)
A = (10 – 3) * 1
A = 7
