\(\Leftrightarrow\dfrac{5\left(2x+15\right)}{45}\ge\dfrac{9\left(2x-1\right)+15x}{45}\)
\(\Leftrightarrow5\left(2x+15\right)\ge9\left(2x-1\right)+15x\)
\(\Leftrightarrow10x+75\ge18x-9+15x\)
\(\Leftrightarrow-21x\ge-84\)
\(\Leftrightarrow x\le\dfrac{84}{21}\)
Vậy \(S=\left\{x|x\le\dfrac{84}{21}\right\}\)
chưa học đến bài nài :>
\(\Rightarrow5\left(2x+15\right)\ge9\left(2x-1\right)+15x\)
\(\Leftrightarrow10x+75\ge18x-9+15x\)
\(\Leftrightarrow-23x\ge-84\)
\(\Leftrightarrow x\ge\dfrac{84}{23}\)