a) Có 40 = 23 . 5
52 = 22 . 13
=> BCNN(40,52) = 23 . 5 . 13 = 520
b) Có 42 = 2.3.7
70 = 2.5.7
180 = 22.32.5
=> BCNN (42,70,180) = 22.32.5.7 = 1260
c) Có 9 = 32
10 = 2.5
11 = 11
=> BCNN (9,10,11) = 32.2.5.11 = 990
Bài làm :
a) Ta có :
\(40=2^3.5\)
\(52=2^2.13\)
BCNN(40;52) = \(2^3.5.13=520\)
b) Ta có :
\(42=2.3.7\)
\(70=2.5.7\)
\(180=2^2.3^2.5\)
BCNN(42;70;180)=\(2^2.3^2.5.7=1260\)
c) Ta có :
\(9=3^2\)
\(10=2.5\)
\(11=11\)
BCNN(9;10;11)=\(2.3^2.5.11=990\)
a) 40 = 23 . 5
52 = 22 . 13 ; BCNN(40, 52) = 23 . 5 . 13 = 520
b) 42 = 2 . 3 . 7
70 = 2 . 5 . 7
180 = 22 . 32 . 5 ; BCNN(42, 70, 180) = 22 . 32 . 5 . 7 = 1260
c) 9 = 32
10 = 2 . 5
11 = 11 ; BCNN(9, 10, 11) = 32 . 2 . 5 . 11 = 990.