Question

determinatinumarul natural n pentru care 2n+2 este divizor a lui 20

Answer 1

n=9 deoarece 2x9+2=18+2=20

Answer 2

2n+2∈D₂₀
2n+2∈{1,2,4,5,10,20}
2n∈{-1,0,2,3,8,18}
n∈{-1/2,0,1,3/2,4,9}
n∈N⇒n∈{0,1,4,9}