Lời giải :
\(BCNN\left(25,42,60\right)=2100\)
\(BCNN\left(120,140,160\right)=3360\)
Bài 1:
25 = 52
42 = 2.3.7
60 = 22.3.5
=> BCNN(25; 42; 60) = 52.3.7.22 = 2100
Bài 2:
120 = 23.3.5
140 = 22.5.7
160 = 25.5
=> BCNN(120; 140; 160) = 25.3.5.7 = 3360
Ta có : 25 = 5^2
42 = 2.3.7
60 = 2^2.3.5
BCNN( 25;42;60 ) = 2^2.3.5^2.7 = 2100
Ta có : 120 = 2^3.3.5
140 = 2^2.5.7
160 = 2^5.5
BCNN ( 120;140;160 ) = 2^5.3.5.7 = 3360