Question

Aflati valorile lui x apartine N, stiind ca elementul 3x+11, 7x+3, 5x-1 apartine multimii A si card A=2

Answer 1

daca cardA=2 ⇒ cate 2 din cele 3 elemente sunt egale

1) 3x+11 = 7x+3
11-3= 7x-3x
8=4x
x=8:4
x=2∈N

2) 3x+11 = 5x-1
11+1 = 5x-3x
12=2x
x=12:2
x=6∈N

3) 7x+3= 5x-1
7x-5x= -1-3
2x=-4
x=-4:2
x=-2∉N

x∈ {2,6}