Question

1.tìm x

a)3|x| -6=2-(-7)

b) (x-1) chia hết (2x+3) cho x lớn hơn hoặc=1

Answer 1

a) \(3\left|x\right|-6=2-\left(-7\right)\)

\(\Leftrightarrow3\left|x\right|-6=2+7\)

\(\Leftrightarrow3\left|x\right|-6=9\)

\(\Leftrightarrow3\left|x\right|=9+6\)

\(\Leftrightarrow3\left|x\right|=15\)

\(\Leftrightarrow\left|x\right|=15:3\)

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

\(\Rightarrow\left[{}\begin{matrix}x=5\\x=-5\end{matrix}\right.\)

Vậy \(x=5\) hoặc \(x=-5\)

Answer 2

b) Ta có:

\(x-1⋮2x+3\)

\(\Rightarrow2\left(x-1\right)⋮2x+3\)

\(\Rightarrow2x-2⋮2x+3\)

\(\Rightarrow\left(2x+3\right)-5⋮2x+3\)

\(\Rightarrow-5⋮2x+3\)

\(\Rightarrow2x+3\in U\left(5\right)=\left\{-1;1;-5;5\right\}\)

\(\Rightarrow\left\{{}\begin{matrix}2x+3=-1\Rightarrow x=-2\\2x+3=1\Rightarrow x=-1\\2x+3=-5\Rightarrow x=-4\\2x+3=5\Rightarrow x=1\end{matrix}\right.\)

Mà \(x\ge1\)

Vậy \(x=1\)