....giúp với mn oiw...............................

`1)`

`a) 5/11 + 23/29 - 16/11`

`= ( 5/11 - 16/11 ) + 23/29`

`= -1 + 23/29`

`= ( -29 + 23 )/29`

`= -6/29`

`b) 13 2/5 + 15/23 + 1 6/10`

`= 67/5 + 15/23 + 8/5`

`= ( 67/5 + 8/5 ) + 13/23`

`= 15 + 15/23`

`= ( 345  + 15 )/233`

`= 360/23`

`c) ( -3/11 : 5/22 ) : ( -15/3 : 26/3 )`

`= ( -3/11 . 22/5 ) : ( -15/3 . 3/26 )`

`= -6/5 : ( -15/26 )`

`= -6/5 . ( -26/15 )`

`= 52/25`

`2)`

`a) ( x - 1/4 )^2 = 4/9`

`=> x - 1/4 = +-2/3`

`=>` $\left[\begin{matrix} x-\dfrac{1}{4}=\dfrac{2}{3}\\ x-\dfrac{1}{4}=\dfrac{-2}{3}\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=\dfrac{2}{3}+\dfrac{1}{4}\\ x=\dfrac{-2}{3}+\dfrac{1}{4}\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=\dfrac{11}{12}\\ x=\dfrac{-5}{12}\end{matrix}\right.$

Vậy `x in { 11/12 ; -5/11 }`

`b) ( x + 0,7 )^3 = -27`

`=> x + 0,7 = -3`

`=> x = -3 - 0,7`

`=> x = -3,7`

Vậy `x = -3,7`

`c) | x - 4/7 | = 1 1/7`

`=> | x - 4/7 | = 8/7`

`=>` $\left[\begin{matrix} x-\dfrac{4}{7}=\dfrac{8}{7}\\ x-\dfrac{4}{7}=\dfrac{-8}{7}\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=\dfrac{8}{7}+\dfrac{4}{7}\\ x=\dfrac{-8}{4}+\dfrac{4}{7}\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=\dfrac{12}{7}\\ x=\dfrac{-4}{7}\end{matrix}\right.$

Vậy `x in { 12/7 ; -4/7 }`

`d) 3^x + 3^( x + 2 ) = 810`

`=> 3^x . 1 + 3^x . 9 = 810`

`=> 3^x . ( 1 + 9 ) = 810`

`=> 3^x . 10 = 810`

`=> 3^x  = 810 : 10`

`=> 3^x = 81`

`=> 3^x = 3^4`

`=> x = 4`

Vậy `x = 4`