12:6+2.7= 2+14= 16

5.4²- 36:3²=80-4=76

`@` `\text {Ans}`

`\downarrow`

`12 \div 6 + 2. 7`

`= 2 + 2.7`

`= 2.(1 + 7)`

`= 2.8`

`= 16`

`5. 4^2 - 36 \div 3^2`

`= 5. 16 - 36 \div 9`

`= 80 - 4`

`= 76`

c) 3⁴ - 5.42

= 81 - 210

= -129

d) 120 : {54 - [50 : 2 - (3² - 2.4)]}

= 120 : {54 - [25 - (9 - 8)]}

= 120 : [54 - (25 - 1)]

= 120 : (54 - 24)

= 120 : 30

= 4

a,   52:4.3+2.52   =   13.3+104  =  39+104  =  143  =  11.13                                                      

b,    5.42-18:32   =  210-9/16  =  3351/16  =  209,4375  (ko phân tích đc)

Bn xem lại đề bài câu b đi, mk thấy sai đề hay sao ý

\(98.42-50\left[\left(18-2^3\right):2+3^2\right]\\ =4116-50\left[\left(18-8\right):2+9\right]\\ =4116-50\left[10:2+9\right]\\ =4116-50\left[5+9\right]\\ =4116-50.14\\ =4116-700\\ =3416\)

98.42-50.[(18-2³):2 +3²]

=98.42-50.[(18-8):2+3²]

=98.42-50.[10:2+3]

=98.42-50.[5+3]

=98.42-50.8

= 4116-400

=3716

=98*42-50*[(18-8):2+9]

=98*42-50*14

=3416

\(a.\sqrt{\left(\sqrt{2}-\sqrt{3}\right)^2}+\sqrt{18}=\left|\sqrt{2}-\sqrt{3}\right|+3\sqrt{2}=\sqrt{3}-\sqrt{2}+3\sqrt{2}\left(\sqrt{3}>\sqrt{2}\right)=\sqrt{3}+2\sqrt{2}\)\(b.3\sqrt{2}-4\sqrt{18}+2\sqrt{32}-\sqrt{50}=3\sqrt{2}-12\sqrt{2}+8\sqrt{2}-5\sqrt{2}=-6\sqrt{2}\)

Giải:

Bài 1:

a) \(6^2\): 4 . 3 + 2 . \(5^2\) 

= 36 : 4 . 3 + 2 . 25

= 27 + 50

= 77

77 = 7 . 11

b) 5 . \(4^2\) - 18 : \(3^2\)

= 5 . 16 - 18 : 9

= 80 - 2

= 78

78 = 2 .3 . 13

Bài 2: 

a) Ta có: \(70⋮x\)

\(84⋮x\)

Do đó: \(x\inƯC\left(70;84\right)\)

\(\Leftrightarrow x\inƯ\left(14\right)\)

\(\Leftrightarrow x\in\left\{1;2;7;14\right\}\)

mà x>8

nên x=14