Bài 1:
a) A = {6;7;8;9;10;11}
B = {8;9;10;11;12;13;14}
b) A ∩ B ={8;9;10;11}
c) A ∩ B có 4 phần tử
Bài 2:
240 = $2^{4}$.3.5
300 = $2^{2}$.5².3
420 = $2^{2}$.3.5.7
⇒ $ƯCLN_{240,300,420}$ = $2^{4}$.3.5².7= 8400
Bài 3:
a) 4.$3^{4}$ - 16 : 2²+2.5³
= 4.81 - 16:4 + 125.2
= (324 - 4) + 250
= 320 + 250 = 570
b)5².3-2².{13 + 5[30 : 2.3-(3³-30.2)]}
=25.3-4.{13 + 5[30 : 2.3-(27-60)]}
=75-4.{13 + 5[15.3-(-33)]}
=75-4.[13 + 5(45+33)]
=75-4(13 + 5.78)
=75-4(13 + 385)
=75 - 4.394
=75 - 1576
=-1571
