Question

Bài 13: Tìm x:
1/ (2x – 15) + 17 = 6
2/ 15 – (4 – 3x) = - 4
3/ - 21 + 3(-x + 7) = -18
4/ 78 : (3x – 2) = -3
5/ -35 : 5.(-3 – 2x) = 35

Answer 1

1 ) ( 2x - 15 ) + 17 = 6

=> 2x - 15 = 6 - 17

=> 2x - 15 = - 11

=> 2x = - 11 + 15

=> 2x = 4

=> x = 4: 2

=> x = 2

Vậy x = 2

2) 15 - ( 4 - 3x ) = -4

=> 4 - 3x = 15 - ( -4 )

=> 4 - 3x = 19

=> 3x = 4 - 19

=> 3x = -15

=> x = -15 : 3

=> x = -5

Vậy x = -5

3) -21 + 3 . ( -x + 7 ) = - 18

=> 3 . ( -x + 7 ) = ( -18 ) - ( -21 )

=> 3 . ( -x + 7 ) = 3

=> -x +7 = 3 : 3

=> -x + 7 = 1

=> -x = 1 - 7

=> -x = - 6

=> x = - (- 6 )

Vậy x = - ( -6 )

4 ) 78 : ( 3x - 2 ) = -3

=> 3x - 2 = 78 : ( -3)

=> 3x - 2 = -26

=> 3x = -26 + 2

=> 3x = -24

=> x = -24 : 3

=> x = -8

Vậy x = -8

5) -35 : 5 . ( -3 - 2x ) = 35

=> -7 . ( -3 ) + 2x = 35

=> -3 + 2x = 35 : ( -7)

=> -3 + 2x = -5

=> 2x = (-5) - (-3)

=> 2x = -2

=> x = -2 : 2

=> x = -

Vậy x = -1

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Answer 2

1/ (2x – 15) + 17 = 6

<=> 2x=4

<=> x=2
2/ 15 – (4 – 3x) = - 4

<=> 3x=-15

<=> x=-5
3/ - 21 + 3(-x + 7) = -18

<=> -3x=-18

<=> x=6
4/ 78 : (3x – 2) = -3

<=> 3x-2=-26

<=> 3x=-24

<=> x=-8
5/ -35 : 5.(-3 – 2x) = 35

<=> -3-2x=-7

<=> 2x=4

<=> x=2

Answer 3

Bài 13:

1/ (2x -15) + 17 = 6

\(\Leftrightarrow\) 2x - 15 = 6 - 17

\(\Leftrightarrow\) 2x - 15 = -11

\(\Leftrightarrow\) 2x = -11 + 15

\(\Leftrightarrow\) 2x = 4

\(\Leftrightarrow\) x = 4 : 2

\(\Leftrightarrow\) x = 2.

Vậy x = 2.

2/ 15 - (4 - 3x) = -4

\(\Leftrightarrow\) 4 - 3x = 15+4

\(\Leftrightarrow\) 4 - 3x = 19

\(\Leftrightarrow\) 3x = 4 - 19

\(\Leftrightarrow\) 3x = -15

\(\Leftrightarrow\) x = -15 : 3

\(\Leftrightarrow\) x = -5.

Vậy x = -5.

3/ -21 + 3(-x + 7 ) = -18

\(\Leftrightarrow\) 3(-x + 7 ) = -18 + 21

\(\Leftrightarrow\) 3(-x + 7 ) = 3

\(\Leftrightarrow\) -x + 7 = 3 : 3

\(\Leftrightarrow\) -x + 7 = 1

\(\Leftrightarrow\) -x = 1 - 7

\(\Leftrightarrow\) -x = -6

\(\Leftrightarrow\) x = 6.

Vậy x = 6.

4/ 78 : (3x - 2) = -3

\(\Leftrightarrow\) 3x - 2 = 78 : (-3)

\(\Leftrightarrow\) 3x - 2 = -26

\(\Leftrightarrow\) 3x = (-26) + 2

\(\Leftrightarrow\) 3x = -24

\(\Leftrightarrow\) x = (-24) : 3

\(\Leftrightarrow\) x = -8.

Vậy x = -8.

5/ -35 : 5.(-3 - 2x) = 35

\(\Leftrightarrow\) (-7).(-3-2x)= 35

\(\Leftrightarrow\) (-3)-2x=35:(-7)

\(\Leftrightarrow\) (-3)-2x=-5

\(\Leftrightarrow\) -2x=(-3)+5

\(\Leftrightarrow\) -2x=2

\(\Leftrightarrow\) x= 2:(-2)

\(\Leftrightarrow\) x=-1.

Vậy x = -1.

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