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résoudre les 3 équations

a) – 2b + 7 = - b + 9
b) 4b – 21 = 7b – 9
c) 7b + 13 = - 3b - 7

merci en avance


Répondre :

Bonjour;

a) – 2b + 7 = - b + 9

7-9 = -b+2b

-2 = b

b) 4b – 21 = 7b –9

-21 +9 = 7b -3b

-12 = 4b

b= -12/4

b = -3

c) 7b + 13 = - 3b - 7

7b+3b = -7-13

10b = -20

b = -20/10 = -2

[tex]bonjour\\\\- 2 b + 7 = - b + 9\\- 2 b + b = 9 - 7 \\- b = 2 \\b = - 2 \\\\4b - 21 = 7 b - 9 \\4 b - 7 b = - 9 + 21 \\- 3 b = 12 \\b = - 4 \\\\7 b + 13 = - 3 b - 7 \\7 b + 3 b = - 7 - 13 \\10 b = - 20\\b = - 2[/tex]