7x.(2+x)-7x.(x+3)=14
7x.[(2+x)-(3+x)]=14
7x.[2+x-3-x]=14
7x.(-1) =14
7x =14:(-1)
7x =-14
x =-14:7
x =-2
Chúc bn học tốt
\(7x\left(2+x\right)-7x\left(x+3\right)=14\)
\(\Leftrightarrow14x+7x^2-7x^2-21x=14\)
\(\Leftrightarrow-7x=14\)\(\Leftrightarrow x=-2\)
Vậy \(x=-2\)