`(3/5+6/4)-5/3`

`=(12/20+30/20)-5/3`

`=42/20-5/3`

`=21/10-5/3`

`=63/30-50/30`

`=13/30`

`2/5 - 3/8 + 7/6 : 7/5`

`= 2/5 - 3/8 + 7/6 xx 5/7`

`= 2/5 - 3/8 +5/6`

`= 1/40+5/6`

`=103/120`

a: =1/2*2/3*...*9/10=1/10

b: =17/32*32/11*11/34=1/2

a) x=11
b) x=2

Bài 3: 

b: \(x\in\left\{3;-3\right\}\)

a: \(A=\sqrt{3}+1-\sqrt{3}+1=2\)

\(B=\dfrac{x+4\sqrt{x}+4-3\sqrt{x}+6-12}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}=\dfrac{x+\sqrt{x}-2}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}=\dfrac{\sqrt{x}-1}{\sqrt{x}-2}\)

b: Để A>2B thì A-2B>0

=>\(\dfrac{2\sqrt{x}-4-\sqrt{x}+1}{\sqrt{x}-2}>0\)

\(\Leftrightarrow\dfrac{\sqrt{x}-3}{\sqrt{x}-2}>0\)

=>x>9 hoặc 0<=x<4

=63.985+157.815+16.7=238.5

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