Question

3. tìm số nguyên x biết

a. 3x-5=-7-13

b. |x|-10=-3

c. x+2(x-9)=0

Answer 1

a. 3x-5=-7-13

3x-5=-20

3x=-20+5

3x=-15

x=-15:3

x=-5

Answer 2

b) |x|-10=(-3)

\(\Leftrightarrow\) |x|=(-3)+10=7

\(\Rightarrow\left[{}\begin{matrix}x=7\\x=-7\end{matrix}\right.\)

Vậy..............

c) x+2(x-9)=0

\(\Leftrightarrow\) (x-9)+2(x-9)=0-9=(-9)

\(\Leftrightarrow\) (x-9)(2+1)=(-9)

\(\Leftrightarrow\) 3(x-9)=(-9)

\(\Leftrightarrow\) x-9=(-9):3=(-3)

\(\Leftrightarrow\) x=(-3)+9=6

Vậy: x=6

Answer 3

\(c.x+2\left(x-9\right)=0\)

\(\Rightarrow x+2x-18=0\)

\(\Rightarrow3x=18\)

\(\Rightarrow x=6\)