bài 1 
a) 4 = 2.2 ; 8 =2.2.2 ; 10=2.5;  18 = 3.3.2 ; 30 =2.5.3 ; 32 = 2^5 ; 48 = 2^4 . 3
Ư(4) = 1; 2;4          Ư(8) = 1;2;4;8                Ư(10) = 1;2;5;10           Ư(18)=1;2;3;6;9;18
Ư(30)= 1;2;3;5;6;15;10;30         Ư(32)=1;2;4;8;16;32             Ư(35) = 1;5;7;35
Ư (48) = 1;2;4;6;8;12;24;48
b) B(6) = 6;12;18;24;30                     B(9)= 9;18;27;36;45;54                    B(11) = 11;22;33;44;55;66
B(20) = 20;40;60;80;100                    B(25) =25;50;75;100;125;150
c) B(15)=105;120;135;150; 165;180;195

Bài 1:a) Ư(4)=1, -1,-2,2,4,-4
Ư(8)=1,-1,2,-2,4,-4,8,-8
Ư(10)=1,-1,2,-2,5,-5,10,-10
Ư(18)=1,-1,2,-2,3,-3,6,-6,9,-9,18,-18
Ư(30)=1,-1,2,-2,3,-3,5,-5,6,-6,10,-10,30,-30
Ư(32)=1,-1,2,-2,4,-4,8,-8,16,-16,32,-32
Ư(35)=1,-1,5,-5,7,-7,35,-35
Ư(48)=1,-1,2,-2,4,-4,6,-6,8,-8,12,-12,24,-24,48,-48
b)B(6)=6,12,18,24,30,...
B(9)=9,18,27,36,45,...
B(11)=11,22,33,44,55,...
B(20)=20,40,60,80,100,...
B(25)=25,50,75,100,125,...
c) B(15)=105,120,135,150,165,180,195 (Lớn hơn 100, nhỏ hơn 200)
Chúc bn học tốt!