Question

Tìm x \(\in\) Z biết :

a) x - 8 = 3x + 4

b) | x | + 15 = 29

c) 17 - | x | = 6

Answer 1

a) x - 8 = 3x + 4

= \(x-3x=4+8\)

= \(-2x=12\)

-> \(x=-6\)

b) | x | + 15 = 29

= | x | = 14

-> \(x=\left\{\begin{matrix}-14\\14\end{matrix}\right.\)

c) 17 - | x | = 6

= | x | = 11

-> x \(x\left\{\begin{matrix}-11\\11\end{matrix}\right.\)

Answer 2

a) x - 8= 3x +4

-8 -4 =3x - x

-12 = 2x

=> 2x = - 12

x = - 12 ; 2

x = - 6

b) \(\left|x\right|\) + 15 =29

\(\left|x\right|\) = 29 -15

\(\left|x\right|\) = 14

=> x = 14 hoặc x = - 14

Vậy : x = 14 hoặc x = `-14

c) 17 - \(\left|x\right|\) = 6

\(\left|x\right|\) = 17 -6

\(\left|x\right|\) = 11

=> x=11 hoặc x= -11

Vậy : x= 11 hoặc x = -11