Question

Determinati cardinalul multimii: M={ n/n€N , si 2n+1/18}
€ este apartine

Answer 1

2n+1∈D18
D18={1,2,3,6,9,18}
2n+1=1⇒2n=1-1⇒n=0
2n+1=2⇒2n=2-1⇒n=1/2
2n+1=3⇒2n=3-1⇒n=1
2n+1=6⇒2n=6-1⇒n=5/2
2n+1=9⇒2n=9-1⇒n=4
2n+1=18⇒2n=18-1⇒n=17/2
M={0,1,4}