\(2x+12=3\left(x-7\right)\)

\(2x+12=3x-21\)

\(2x-3x=-21-12\)

          \(-x=-33\)

              \(x=33\)

\(\Leftrightarrow2x+12=3x-21.\)

\(\Leftrightarrow2x-3x=-21-12\)

\(\Leftrightarrow-x=-33\)

\(\Rightarrow x=33\)

Vậy \(x=33\)

2x²-1=49

Bài 1 :

2x + 12 = 3 . ( x - 7 )

2x + 12 = 3x - 21

 2x - 3x = - 21 - 12

        - x = - 33

=> x = 33

Vậy x = 33

bài 2 bn tự làm nha

mk chỉ biết làm bài 1 thôi

a. 9 - 35 = (17 - x) - (35 + 17)

=> -26 = 17 - x - 52

=> x = 17 - 52 + 26

=> x = -9

b. -7 - (12 + x) = -(-14 + 3) - (2x - 7)

=> -7 - 12 - x = - (-11) - 2x + 7

=> -19 - x = 11 + 7 - 2x

=> 2x - x = 18 + 19

=> x = 37

Thảo Jackson : nham

\(a,2x+12=3\left(x-7\right)\)

\(2x+12=3x-21\)

\(2x-3x=-21-12\)

\(-x=-33\)

\(x=33\)

\(b,\left|-9-x\right|-5=12\)

\(\left|-9-x\right|=17\)

\(\Rightarrow\orbr{\begin{cases}-9-x=17\\-9-x=-17\end{cases}\Rightarrow\orbr{\begin{cases}x=-26\\x=8\end{cases}}}\)

\(\text{a) 2x + 12 = 3(x-7)}\)

\(\Rightarrow2x+12=3x-3.7\)

\(\Rightarrow2x+12=3x-21\)

\(\Rightarrow2x+12+21=3x\)

\(\Rightarrow2x+33=3x\)

\(\Rightarrow3x-2x=33\)

\(\Rightarrow x\left(3-2\right)=33\)

\(\Rightarrow x=33\left(tm\right)\)

Vậy x =33

a) 2x+12=3(x-7)

2x+12=3x-21

2x-3x=-12-21

-x=-33

x=33

Vậy x=33

b) |-9-x|-5=12

|-9-x|=12+5

|-9-x|=17

\(\Rightarrow\orbr{\begin{cases}-9-x=-17\\-9-x=17\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=8\\x=-26\end{cases}}\)

Vậy x\(\in\){8;-26}