Question

determinati : a) x-1 € D15 ; b) 2x+1 € D12 ; c) x+2 € D21

Answer 1

a) x- 1 apartine D15 {1,3,5,15} | +1
x apartine { 2,4,6,16}

b) 2x+1 apartine D12 { 1,2,3,4,6,12} | -1
2x apartine {0,1,2,3,5,11} | :2
x apartine { 0,1} 
c) x+2 apartine D21 { 1,3,7,21} | -2
x apartine { -1,1,5,19}