\(\dfrac{12}{17}+\left(\dfrac{-6}{19}\right)+\dfrac{5}{17}+\left(\dfrac{-13}{19}\right)-\dfrac{1}{2}=\left(\dfrac{12}{17}+\dfrac{5}{17}\right)+\left(\dfrac{-6}{19}+\dfrac{-13}{19}\right)-\dfrac{1}{2}=1+\left(-1\right)-\dfrac{1}{2}=0-\dfrac{1}{2}=-\dfrac{1}{2}\)

` 12/17 + ( -6/19) + 5/17 + ( -13/19 ) -1/2 = ( 12/17 + 5/7 ) + ( -6/16 + -13/19) - 1/2 = 1 + ( -1) -1/2 = 0 - 1/2 = -1/2 `

\(=\left(\dfrac{5}{17}+\dfrac{12}{17}\right)+\left(\dfrac{-13}{19}+\dfrac{-6}{19}\right)-\dfrac{1}{2}=\dfrac{17}{17}+\left(-\dfrac{19}{19}\right)-\dfrac{1}{2}\)

\(=1+\left(-1\right)-\dfrac{1}{2}=-\dfrac{1}{2}\)

giúp mình đi mọi người

5/6-x=2/3

x=5/6-2/3

x=1/6

4/3:x=2

x=4/3:2

x=2/3

a) x = 1/6

b) x = 2/3

a) \(\dfrac{2}{5}\cdot x=\dfrac{1}{2}+\dfrac{6}{8}\)

    \(\dfrac{2}{5}\cdot x=\dfrac{5}{4}\)

          \(x=\dfrac{5}{4}\div\dfrac{2}{5}\)

          \(x=\dfrac{25}{8}\)

b) \(\dfrac{20}{7}-x=\dfrac{19}{7}\div\dfrac{3}{2}\)

    \(\dfrac{20}{7}-x=\dfrac{19}{7}\cdot\dfrac{2}{3}\)

    \(\dfrac{20}{7}-x=\dfrac{38}{21}\)

             \(x=\dfrac{20}{7}-\dfrac{28}{21}\)

             \(x=\dfrac{22}{21}\)

a) x=25/8

b)=22/21

a) x=25/8

b)=22/21

Câu a,b  hình như nhầm đề mình tự sửa nha ;-;

a, Ta có : \(\left(x^2-x-6\right)^2+\left(x-3\right)^2\)

\(=\left(x^2-3x+2x-6\right)^2+\left(x-3\right)^2\)

\(=\left(x-3\right)^2\left(x+2\right)^2+\left(x-3\right)^2\)

\(=\left(x-3\right)^2\left(\left(x+2\right)^2+1\right)\)

b, Ta có : \(\left(x^2-x-20\right)^2+\left(x+4\right)^2\)

\(=\left(x^2+4x-5x-20\right)^2+\left(x+4\right)^2\)

\(=\left(x+4\right)^2\left(x-5\right)^2+\left(x+4\right)^2\)

\(=\left(x+4\right)^2\left(\left(x-5\right)^2+1\right)\)

\(\dfrac{6^x}{3^3\cdot4}=2\)

=>6^x=2*4*3^3=8*3^3=6^3

=>x=3

\(9+4\sqrt{2}=\left(2\sqrt{2}+1\right)^2\)

\(\Rightarrow6x-36=72\\ \Rightarrow6x=108\\ \Rightarrow x=18\)

6x-36=72

6x=72+36

6x=108

x=108:6

x=18

\(x=18\)