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2013-01-26T21:25:19+01:00

1) 16 x²+9 = 16 x²- 56 x +2x -7

                9=  - 56 x+ 2x -7

                16= -54 x

                 - x = 0,30

                   x= -o,30

 

 

Voila pour le premier

 

Meilleure réponse !
2013-01-26T21:51:03+01:00

Bonsoir

1)

(4x+3)² = (8x+1)(2x-7)

16x²+9 +24x = 16x² -56x +2x -7 

24x +56x-2x = -7 -9

78x = -16

x = -16/78 = - 4/17

2)

(7x+2)² = (3x-5)² 

(7x+2)² -(3x-5)² =0  forme de a²-b² =(a-b)(a+b) 

(7x+2-3x+5)(7x+2+3x-5) = 0

(4x+7)(10x-3) =0   si un des facteurs = 0

4x+7 = 0 si x = -7/4

10x-3 = 0 si x = 3/10 

3)

1/x -1 +2/x +2 = 0

3/x +1 =0

3/x = -1 

x =-3