Bài 1
1. a) Tìm `ƯCLN (350; 490)`
Ta có: `350=2.5^2. 7`
`490=2.5.7^2`
=>`ƯCLN (350; 490)=2.5.7=70`
Vậy `ƯCLN (350; 490)=70`
b) Tìm `BCNNNN (18; 45)`
Ta có:`18=3^2. 2`
`45=3^2 . 5`
=>`BCNNNN (18; 45)=3^2. 2 . 5=90`
Vậy `BCNNNN (18; 45)=90`
2.
a) `157.2009 - 57.2009`
`=2009.(157-57)=2009.100=200900`
b) `5^2. 3^3 + 5^2. 72+5^2`
`=5^2.(27+72+1)=25.100=2500`
c) `( 100 - 97)^2 + 7^7 : 7^5 + 2010^0`
`=3^2 + 7^7: 7^5 + 2010^0`
`=9+7^2+1`
`=9+49+1=59`