Question

Scrieti elementele multimilor: 
A={x apartine lui N\ {0,1} | 6 divizibil cu (x-1)} si 
B={x apartine lui N | x < 19 si 4 | x + 6}.
URGENTTTTTTTTTTTTTTTTTTTTTT!!!!!! VA ROG

Answer 1

x-1∈D6
D6={1,2,3,6}
x-1=1⇒x=1+1⇒x=2
x-1=2⇒x=3
x-1=3⇒x=4
x-1=6⇒x=7
A={2,3,4,7}
x+6∈D4
D4={1,2,4}
x+6=1⇒x=1-6=-5∉N
x+6=2⇒x=-4∉N
x+6=4⇒x=-2∉N
B=Ф