Question

Rezolvati in N
1. 5+2x=81
2. 6x+3=21
3. 4(x+3)+1=25
4. 5x mai mic decat 62
5.  4x+3≤11
6.2x-3 mai mic decat 4

Answer 1

1)  2x = 81 - 5 ⇔ 2x = 76 ⇔x = 76: 2 ⇔  x = 38 ∈ N
2)   6x = 21 - 3 ⇔ 6x = 18 ⇔ x = 18: 6 ⇔x = 3 ∈ N
3) 4x + 12 +1 = 25 ⇔ 4x +13 = 25 ⇔4x = 25 - 13 ⇔ 4x = 12 ⇔ x = 12:4
   x = 3 ∈N
4) 5x < 62 ⇔ x < 62/5 ⇔ x∈ ( - infinit, 62/5) , 62/5∉N
5) 4x ≤11 - 3 ⇔ 4x ≤ 8 ⇔ x ≤ 8:4 ⇔ x ≤2 ∈ N, x ∈ ( - infinit, 2 }
6) 2x - 3 < 4 ⇔ 2x < 4 +3 ⇔ 2x < 7 ⇔ x < 7/2 ∉N , x ∈( - infinit, 7/2)

Answer 2

5+2x=81
2x=76
x=76:2=38



6x+3=21
6x=21-3
6x=18
x=18:6=3



4(x+3)+1=25
4x+12+1=25
4x=25-12-1
4x=12
x=3



5x<62
x<62:5
x<12,4
x={0,1,2,3,4,5,6,7,8,9,10,11,12}



4x+3<sau=11
4x<sau=11-3
4x<sau=8
x<sau=2
x={0,1,2}



2x-3<4
2x<4+3
2x<7
x<7:2
x<3,5
x={0,1,2,3}



Sper sa fie bine