Question

Determinați mulțimile A ={x e N / 2x + 5 e D45

Answer 1

D45={1,3,5,9,15,45}
2x+5=1
2x=1-5
2x=-4
x=-2

2x+5=3
2x=3-5
2x=-2
x=-1

2x+5=5
x=0

2x+5=9
2x=4
x=2

2x+5=15
2x=10
x=5

2x+5=45
2x=40
x=20

A={-2;-1;0;2;10;20}