Question

A={x Ix ∈ N  si (x-1) I 11;

B={ xI x∈ N si (x + 1) I 16

Answer 1

x-1∈D11
x-1=1⇒x=2
x-1=11⇒x=12
A={2,12}
x+1∈D12
D12={1,2,3,4,12}
x+1=1⇒x=0
x+1=2⇒x=1
x+1=3⇒x=2
x+1=4⇒x=3
x+1=12⇒x=11
B={0,1,2,3,11}