Bài 2: 

Ta có: \(x\left(x-4\right)-x^2+8=0\)

\(\Leftrightarrow x^2-4x-x^2+8=0\)

\(\Leftrightarrow-4x=-8\)

hay x=2

1)=x²-49-x²

=-49

2)=>x²-4x-x²+8=0

=>-4x+8=0

=>-4x=-8

=>x=2

x^3+1=9

x^3=8

x^3=2^3

=>x=2

=>x³=8

hay x=2

\(x+x.\dfrac{1}{3}+3y=\dfrac{1}{5}\)

\(x.\dfrac{4}{3}+3y=\dfrac{1}{5}\)

\(x.\dfrac{4}{3}=\dfrac{1}{5}-3y\)

\(x=\left(\dfrac{1}{5}-3y\right):\dfrac{4}{3}=\dfrac{3}{20}-\dfrac{9y}{4}\)

`x-1/8=1/4xx2/3`

`x-1/8=1/6`

`x=1/6+1/8`

`x=7/24`

x - 1/8 = 1/6

x         = 6/48 + 8/48
x         = 14/48

\(\Leftrightarrow x+\dfrac{1}{8}=\dfrac{1}{6}\\ \Leftrightarrow x=\dfrac{1}{24}\)

\(\Rightarrow x+\dfrac{1}{8}=\dfrac{1}{6}\\ \Rightarrow x=\dfrac{1}{24}\)

\(x-\dfrac{1}{4}=\dfrac{-21}{10}\)

\(x=\dfrac{-21}{10}+\dfrac{1}{4}\)

\(x=\dfrac{-42}{20}+\dfrac{5}{20}=\dfrac{-37}{20}\)

\(\Leftrightarrow x^3+2x^2-3x-x^3-3x^2=-4\)

\(\Leftrightarrow x^2+3x-4=0\)

=>(x+4)(x-1)=0

=>x=-4 hoặc x=1

x : 1/3 = 1/2 +1/3

=>x:1/3=5/6

=>x=5/6 x 1/3

=>x=5/18

(x:2/3):2/5=7/10

=>x:2/3=7/10 x 2/5 

=>x:2/3=7/25

=>x=7/25x2/3

=>x=14/75

CHÚC BẠN HỌC TỐT

cái này vừa gửi rồi mà:D

x:1/3=1/2+1/3
x:1/3=5/6
x      =5/6.1/3
x      =5/18
 

(x:2/3):2/5=7/10
x:2/3        =7/10.2/5
x:2/3        =7/25
x:2/3        =7/25.2/3
x:2/3        =14/75
 

1) \(x:\dfrac{1}{3}=\dfrac{1}{2}+\dfrac{1}{3}\)

\(\Rightarrow3\times x=\dfrac{5}{6}\Rightarrow x=\dfrac{5}{18}\)

2) \(\left(x:\dfrac{2}{3}\right):\dfrac{2}{5}=\dfrac{7}{10}\)

\(\Rightarrow\dfrac{3}{2}\times x=\dfrac{7}{10}\times\dfrac{2}{5}=\dfrac{7}{25}\)

\(\Rightarrow x=\dfrac{7}{25}:\dfrac{3}{2}=\dfrac{14}{75}\)

X : 1/3 = 1/2 + 1/3 

X = 5/18

( X : 2/3 ) : 2/5 = 7/10

X = 14/75