Bonjour
1-Développer et réduire :
A=100x² -9 +(10x-3)(-10x+7)
A = 100x² - 9 - 100x² + 70x + 30x - 21
A = 100x² - 100x² + 70x + 30x - 9 - 21
A = 100x - 30
2- Factoriser A
A=100x² -9 +(10x-3)(-10x+7)
A = (10x)² - (3)² + (10x - 3) (- 10x + 7)
A = 10 (10x - 3)
3-Calculer A pour x= -9/7
A = 100x - 30
A = 100 * (- 9/7) - 30
A = - 900/7 - 30
A = - 900/7 - 210/7
A = - 1 110/7
4-Résoudre l'équation A=0
A = 10 (10x - 3)
A = 10 (10x - 3) = 0
10x - 3 = 0
10x = 3
x = - 3/10.
