Đáp án:

Giải thích các bước giải:

 Ta có:

Bài `7:`

`a) 20-[30-(6-1)^2 ]`

`= 20-[30-5^2 ]`

`= 20-(30-25)`

`=20-5`

` =15`

`---`

`b) 20-[30-(5-1)^2 ]`

`=20-[30-4^2 ]`

`= 20-(30-16)`

`=20-14` 

`=6`

`----`

`c) 50-[30-(6-2)^2 ]`

`=50-[30-4^2 ]`

`=50-(30-16)`

`=50-14`

`=36`

`----`

`d) 100-[75-(7-2)^2 ]`

`=100-[75-5^2 ]`

`=100-(75-25)`

`=100-50`

`=50`

`----`

Bài `8:`

`a) 32-6.(8-2^3 )+18`

`=32-6.(8-8 )+18`

`=32-6.0+18`

`=50-0`

`=50`

`----`

`b) (3.5-9)^3 . (1+2.3)^2 +4^2`

`= (15-9)^3 . (1+6)^2  +16`

`=6^3 . 7^2 +16`

`=216. 49+16`

`=10584+16`

`=10600`

`---`

`c) 9234:[3.3.(1+8^3 )]`

`=9234:[9.(1+512 )]`

`=9234:(9.513)`

`=9.513.2:(9.513)`

`=9.513.2:9:513`

`=2`

`---`

`d) 76-{2.[1.5^2 -(31-2.3)]}+3.25`

`=76-{2.[1.25-(31-6)]}+75`

`=76-[2.(25-25)]+75`

`=2.0+151`

`=0+151`

`=151`