Tìm số nguyên x, biết: a)250:( x- 5) = 64-14 b. 3.( x+8)=17 +(- 23) c. 2.( x+3)^2= ( -3)^2 -1

`a) 250 : ( x - 5 ) = 64 -  14`

`⇒ 250 : ( x - 5 ) = 50`

`⇒ x - 5 = 250 : 50`

`⇒ x - 5 = 5`

`⇒ x = 5 + 5`

`⇒ x = 10`

Vậy `, x = 10 .`

`b) 3 . ( x + 8 ) = 17 + ( - 23 )`

`⇒ 3 . ( x + 8 ) = - 6`

`⇒ x + 8 = - 6 : 3`

`⇒ x + 8 = - 2`

`⇒ x = - 2 - 8`

`⇒ x = - 10`

Vậy `, x = - 10 .`

`c) 2 . ( x + 3 )^2 =  ( - 3 )^2 - 1`

`⇒ 2 . ( x + 3 )^2 = 9 - 1`

`⇒ 2 . ( x + 3)^2 = 8`

`⇒ ( x + 3 )^2 = 8 : 2`

`⇒ ( x + 3 )^2 = 4`

`⇒` \(\left[ \begin{array}{l}( x + 3 )^2 = 2^2\\( x + 3 )^2 = ( - 2 )^2\end{array} \right.\) 

`⇒` \(\left[ \begin{array}{l}x + 3 = 2\\x + 3 = - 2\end{array} \right.\) 

`⇒` \(\left[ \begin{array}{l}x = - 1\\x = - 5\end{array} \right.\) 

Vậy `, x ∈ { - 1 ; - 5 }`