Question

Bài 3. Tìm x biết: 
1) |x| = 10                                     2) |x - 8| = 0                               3) 7 + |x| = 12             
4) |x + 1| = 3                                 5) 15 - x = 16 - (14 - 42)           6) 210 - (x - 12) = 168  

Answer 1

1 , 10

2 , 8

3 , 5

4 , 2

5 , 1

6 ,

Answer 2

1/ `|x|=10<=> x=\pm 10`

2/ `|x-8|=0<=>x-8=0<=>x=8`

3/ `7+|x|=12<=>|x|=5<=>x=\pm 5`

4/ `|x+1|=3`

$\Leftrightarrow\left[\begin{array}{1}x+1=3\\x+1=-3\end{array}\right.\\\Leftrightarrow\left[\begin{array}{1}x=3\\x=-4\end{array}\right.$

5/ `15-x=16-(14-42)`

`<=>15-x=16+28`

`<=>15-x=44`

`<=>x=-29`

6/ `210-(x-12)=168`

`<=>210-x+12=168`

`<=>222-x=168`

`<=>x=54`

Answer 3

1.

\(\left|x\right|=10\Leftrightarrow x=\pm10\)

2.

\(\left|x-8\right|=0\Leftrightarrow x-8=0\Leftrightarrow x=8\)

3.

\(7+\left|x\right|=12\Leftrightarrow\left|x\right|=5\Leftrightarrow x=\pm5\)

Answer 4

4.

\(\left|x+1\right|=3\Leftrightarrow x+1=\pm3\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-4\end{matrix}\right.\)

5.

\(15-x=16-\left(14-42\right)\Leftrightarrow15-x=44\Leftrightarrow x=-29\)

Answer 5

6.

\(210-\left(x-12\right)=168\)

\(\Leftrightarrow x-12=42\)

\(\Leftrightarrow x=54\)

Answer 6

1. x = \(\pm\)10

6. 210 - (x - 12) = 168

<=> 210 - x + 12 = 168

<=> 210 + 12 - 168 = x

<=> x = 54

Answer 7

1: Ta có: |x|=10

nên \(x\in\left\{10;-10\right\}\)

2: Ta có: |x-8|=0

\(\Leftrightarrow x-8=0\)

hay x=8

3: Ta có: \(\left|x\right|+7=12\)

\(\Leftrightarrow\left|x\right|=5\)

hay \(x\in\left\{5;-5\right\}\)

Answer 8

4: Ta có: \(\left|x+1\right|=3\)

\(\Leftrightarrow\left[{}\begin{matrix}x+1=3\\x+1=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-4\end{matrix}\right.\)

5: Ta có: \(15-x=16-\left(14-42\right)\)

\(\Leftrightarrow15-x=16-14+42\)

\(\Leftrightarrow15-x=44\)

hay x=-29

6: Ta có: \(210-\left(x-12\right)=168\)

\(\Leftrightarrow x-12=42\)

hay x=54