a) x≤7⇒x∈(-α,7}
2x+1,2x+2,2x+3=x(2+1,2+2,2)+3=5,4x+3
daca x=-2⇒5,4·(-2)+3=-10,8+3=-7,8
x=-1⇒5,4·(-1)+3=-2,4
x=0⇒5,4·0+3=3
.........
A={.......-7,8; -2,4; 3;8,4; 13,8; 19,2; 24,6; 30; 35,4; 40,8}
b) B={4,5,6,7,8,9}
c)C={7,8,9,10,11,12,13,14}
d)D={11,12,13,14,15,16,17,18,19,20,21,22,23}
e)x∈D18
D18={1,2,3,6,9,18}
E={1,2,3,6,9,18}
f)F={1,3,5,7,9,11,13}