Verified answer

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3 x - 2/7 ≤  3 x /2 - 4

42 x /14 - 21 x /14 ≤ - 56/14 + 4/14

21 x /14 ≤ - 52/14

21 x ≤ - 52

x ≤ -  52/21

] - ∞ : - 52/21 ]

f ( 0) =  - 4 et  f ( - 3 ) = 0

( 0 - 4 ) / ( - 3 - 0 ) =   4/3

f ( - 3) = 0

- 12/3 + b = 0

- 4 + b = 0

b =  4

f(x) =  4 x /3 + 4

4 x /3 + 4 ≥ -  3

4 x /3 ≥ - 9/3 - 12/3

4 x ≥  - 21 / 3

4 x ≥ - 7

x ≥ - 7/4

[ - 7/4 :  + ∞ [