Question

Determinati n apartine lui N pentru care 15 supra 2n+1 apartine lui N

Answer 1

2n = -1-15
2n= -16
n= -16
n=-8

Answer 2

15/2n+1 ∈N ⇒2n+1∈D15 (divizorii lui 15)
D15={1,3,5,15}
2n+1=1⇒2n=0⇒n=0⇒n∈N
2n+1=3⇒2n=3-1⇒2n=2⇒n=1⇒n∈N
2n+1=5⇒2n=5-1⇒2n=4⇒n=2⇒n∈N
2n+1=15⇒2n=15-1⇒2n=14⇒n=7⇒n∈N
n∈{0,1,2,7}