\(A=\frac{12n+1}{2n+3}\)
\(\Leftrightarrow A=\frac{12n+18-17}{2n+3}\)
\(\Leftrightarrow A=\frac{6\left(2n+3\right)-17}{2n+3}\)
\(\Leftrightarrow A=\frac{6\left(2n+3\right)}{2n+3}-\frac{17}{2n+3}\)
\(\Leftrightarrow A=6-\frac{17}{2n+3}\)
Với A=-11 ta có :
\(6-\frac{17}{2n+3}=-11\)
\(\Leftrightarrow\frac{17}{2n+3}=6--11\)
\(\Leftrightarrow\frac{17}{2n+3}=17\)
\(\Leftrightarrow2n+3=1\)
\(\Leftrightarrow2x=-2\)
<=>x=-1