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Sagot :

MAUDMARINE

Bonjour

a. 2x + 4 = - x + 28

2x + x = 28 - 4

3x = 24

x = 24/3

x = 8

b. 10x + 3 = 5x + 45

10x - 5x = 45 - 3

5x = 42

x = 42/5

x = 8,4

c. x² + 2x + 20 = 100

x² + 2x + 20 - 100 = 0

x² + 2x - 80 = 0

(x - 8) (x + 10) = 0

x - 8 = 0          ou        x + 10 = 0

x = 8                            x = - 10

d. - 2x² + 8 = - 15x

- 2x² + 8 + 15x = 0

-(x - 8) (2x + 1) = 0

x - 8 = 0          ou           2x + 1 = 0

x = 8                               2x = - 1

                                       x = - 1/2

Marion a tort.

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