Suprime les parenthèse puis réduit aider moi svpl A=a-(a-b) D=4x²-5x+7-(5x²-7x+9) B= b+(a-b-3)

Bonjour.

A = a - (a - b)
A = a - a + b
A = b.

D = 4x² - 5x + 7 - (5x² - 7x + 9)
D = 4x² - 5x + 7 - 5x² + 7x - 9
D = 4x² - 5x² - 5x + 7x + 7 - 9
D = - x² + 2x - 2.

B = b + (a - b - 3)
B = b + a - b - 3
B = b - b + a - 3
B = a - 3.

Bonne journee !

A = a - (a - b)
A = a - a + b
A = b

D = 4x² - 5x + 7 - (5x² - 7x + 9)
D = 4x² - 5x + 7 - 5x² + 7x - 9
D = 4x² - 5x² - 5x + 7x + 7 - 9
D = - x² + 2x - 2

B = b + (a - b - 3)
B = b + a - b - 3
B = b - b + a - 3
B = a - 3