\(-3+11>-5x+21\)
\(\Leftrightarrow-3+11+5x-21>0\)
\(\Leftrightarrow-13+5x>0\)
\(\Leftrightarrow5x>13\)
\(\Leftrightarrow x>\dfrac{13}{5}\)
\(-8>-5x+21\\ =>-5x+21< -8\\ =>5x< -8-21\\ =>5x< -29\\ =>x< -\dfrac{29}{5}\)
\(-3+11>-5x+21\)
\(\Leftrightarrow5x>21-11+3\)
\(\Leftrightarrow5x>13\)
\(\Leftrightarrow x>\dfrac{13}{5}\)
Vậy \(S=\left\{x|x>\dfrac{13}{5}\right\}\)
\(\Leftrightarrow8>-5x+21\\ \Leftrightarrow8-21>-5x\\ \Leftrightarrow-13:-5< x\\ \Leftrightarrow x>\dfrac{13}{5}\)
