Hướng dẫn giải:

Khoanh vào A. 18 x 2 + 10.

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

A

A

A

a: \(=\sqrt{3}-\sqrt{2}+3\sqrt{2}=2\sqrt{2}+\sqrt{3}\)

1)
a) \(34,2:36=0,95\)
b) \(36,18:18=2,01\)
c) \(5,05:25=0,202\)
d) \(17,25:75=0,23\)
2) 
a) \(75,52:32=2,36\)
b) \(4,68:13=0,36\)
c) \(81,6:34=2,4\)
d) \(134,4:42=3,2\)
3) 
a) \(882:36=24,5\)
b) \(78:24=3,25\)
c) \(3:15=0,2\)
d) \(15:75=0,2\)
4) 
a) \(3:75=0,04\)
b) \(750:300=2,5\)
c) \(390:12=32,5\)
d) \(54:24=2,25\)

\(\dfrac{18}{17}:9=\dfrac{18}{17}\times\dfrac{1}{9}=\dfrac{18}{153}=\dfrac{2}{17}\)

\(\dfrac{8}{5}-\dfrac{18}{27}=\dfrac{216}{135}-\dfrac{90}{135}=\dfrac{126}{135}=\dfrac{14}{15}\)

\(\dfrac{2}{7}+\dfrac{5}{9}=\dfrac{18}{63}+\dfrac{35}{63}=\dfrac{53}{63}\)

`18/17:9 = 18/17 xx 1/9 =  2/17 `

`8/5-18/27     = 216/135 - 90/135 = 126/135 = 14/15 `    

` 2/7+5/9 = 18/63 + 35/63 =53/63`

\(\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{20}}{\dfrac{19}{1}+\dfrac{18}{2}+\dfrac{17}{3}+....+\dfrac{1}{19}}\)

\(=\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{20}}{1+\left(\dfrac{18}{2}+1\right)+\left(\dfrac{17}{3}+1\right)+\left(\dfrac{1}{19}+1\right)}\)

\(=\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+...+\dfrac{1}{20}}{1+\dfrac{20}{2}+\dfrac{20}{3}+...+\dfrac{20}{19}}\)

\(=\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+...+\dfrac{1}{20}}{20.\left(\dfrac{1}{2}+\dfrac{1}{3}+...+\dfrac{1}{19}+\dfrac{1}{20}\right)}\)

\(=\dfrac{1}{20}\)

18 x 4,5 + 18 x 33,5 - 2 x 18 x 9 

= 18 x 4,5 + 18 x 33,5 - 18 x 18

= 18 x (4,5 + 33,5 - 18)

= 18 x 20

= 360

= 324 nha

mk nham nha = 360