Trường hợp 1: x+2 chia hết cho 10→(x+2)∈ B(10)={0; ±10; ±20; ±30; ±40; ...}
⇒(x+2)∈{0; ±10; ±20; ±30; ±40;...}→x∈{0-2; ±10-2; ±20-2; ±30-2; ±40-2;...}→x∈{-2; -12; 18; -22; 28; -32; 38;...}
Mà x<500 nên x∈{-2; -12; 18; -22; 28; -32; 38;...; 458; -462; 468; -472; 478; -482; 488; -492; 498; -502}
Trường hợp 2: x+2 chia hết cho 15→(x+2)∈ B(15)={0; ±15; ±30; ±45; ...}
⇒(x+2)∈{0; ±15; ±30; ±45;...}→x∈{0-2; ±15-2; ±30-2; ±45-2;...}→x∈{-2; -17; 12; -32; 28; -47; 43;...}
Mà x<500 nên x∈{-2; -17; 12; -32; 28; -47; 43;...;448; -452; 463; -467; 478; -482; 493; -497}
Trường hợp 3: x+2 chia hết cho 25→(x+2)∈ B(25)={0; ±25; ±50; ±75; ...}
⇒(x+2)∈{0; ±25; ±50; ±75;...}→x∈{0-2; 25-2; ±50-2; ±75-2;...}→x∈{-2; -27; 22; -52; 58; -77; 73;...}
Mà x<500 nên x∈{-2; -27; 22; -52; 58; -77; 73;...;448; -452; 473; -477; 498; -502}
