➡A = { x | x € N si 2x <= 7 }
2x <= 7 ; x € N => x = { 0, 1, 2, 3, ... }
⛅ x = 0 ✨
2 x 0 <= 7
0<= 7 " A "
⛅ x = 1 ✨
1 x 2 <= 7
2 <= 7 " A"
⛅ x = 2 ✨
2 x 2 <= 7
4 <= 7 " A "
⛅ x = 3 ✨
3 x 2 <= 7
6 <= 7 "A"
⛅ x = 4 ✨
4 x 2 < = 7
8 <= 7 " F "
=> x € { 0, 1, 2, 3} ☑
✏B = { x | x €N si x + 2 < 5 }
x + 2 < 5
x < 5 - 2
x < 3
x € { 0, 1, 2 }
⚡Verificare:
- 0 + 2 < 5 => 2 < 5 " A"
- 1 + 2 < 5 => 3 < 5 "A"
- 2 + 2 < 5 => 4 < 5 " A"
- 3 + 2 < 5 => 5 < 5 "F"
=> x € { 0, 1, 2 } ✔
