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determinati numerele naturale x care verifică relatia 2x -11<7

Răspuns :

2x -11< 7   | +11
2x < 18  | :2
x < 9
 x ∈  N => x ∈ {0,1,2,3,4,5,6,7,8}


2 x - 11 < 7

2 x < 7 + 11 

2 x < 18 

x < 18 : 2 

x < 9 ⇒  x ∈ { 0, 1, 2, 3, 4, 5, 6, 7, 8 } ∈ N

Verific:

x = 0 ⇒ 2×0 -11 <7

x=1 ⇒ 2×1 -11 = -9 <7

x = 6 ⇒ 2 × 6 - 11 = 12 - 11 = 1 < 7 

x = 7 ⇒ 2 × 7 - 11 = 14 - 11 = 3 < 7 

x = 8 ⇒ 2 × 8 - 11 = 16 - 11 = 5 < 7