1: Tính hợp lí a) 195:[12.(13^2 - 80 : 2) - 69] b)72.13+28.5+72.17+28.25 c)65.111-13.15:37 2:Tìm x a) (x:15-10).23-160=300 b) x-13-3.x+14=54 c) 1000.[50-(2^x - 6)] =4^2 + 3^2

`#Mâyy `

Bài `1 :`

`a)195:[12. (13^2- 80 :2)-69]`

`= 195 : [12 . (169 - 40)-69]`

`=195 :  (12 . 129 -69)`

`= 195/1479`

`b) 72.13 + 28 . 5 + 72 . 17 + 28.25`

`=72.(12+17) + 28. (5+25)`

`=72.30 + 28.30`

`=(72+28).30`

`=100.30`

`=3000`

`c)65.111-13.15:37`

`=65.111-13.5.3:37`

`=65.111-65.5:37`

`= 65 . (111xx3:37)`

`=65 x 9`

`=585`

Bài `2 :`

`a) (x:15-10).23-160=300 `

`=>`(x:15-10).23=300 + 160`

`=>(x:15-10).23=460`

`=>x:15-10=460:23`

`=>x:15-10=20`

`=>x:15=20+10`

`=>x:15=30`

`=>x=30:15`

`=>x=2`

Vậy`, x=2

`b) x.13-3.x+14=54`

`=>x.(13-3)=54-14`

`=>x.10=40`

`=>x=40:10`

`=>x=4`

Vậy`, x=4`

`c) 1000:[50-(2^x-6]=4^2+3^2 `

`=>1000:[50-(2^x-6]=16+9`

`=>1000:[50-(2^x-6]=25`

`=>50-(2^x - 6)]       = 1000 : 25

`=>50-(2^x - 6)]         =40

`=>2^x-6                  =50-40`

`=>2^x-6                   =10`

`=>2^x                      =10+6`

`=>2^x                      =16`

`=>2^x                      =2^4`

`=>x=4`

`Vậy,x=4`