$a) \dfrac{x-23}{24}+\dfrac{x-23}{25}=\dfrac{x-23}{26}+\dfrac{x-23}{27}$
$\to \dfrac{x-23}{24}+\dfrac{x-23}{25}-\dfrac{x-23}{26}-\dfrac{x-23}{27}=0$
$\to (x-23)(\dfrac{1}{24}+\dfrac{1}{25}-\dfrac{1}{26}-\dfrac{1}{27}=0$
Do: $\dfrac{1}{24}+\dfrac{1}{25}-\dfrac{1}{26}-\dfrac{1}{27}\ne0$
$\to x-23=0$
$\to x=23$
Vậy $S$={23}
$b) \dfrac{x+2}{98}+1+\dfrac{x+3}{97}+1=\dfrac{x+4}{96}+1+\dfrac{x+5}{95}+1$
$\to \dfrac{x+2+98}{98}+\dfrac{x+3+97}{97}-\dfrac{x+4+96}{96}-\dfrac{x+5+95}{95}=0$
$\to (x+100)(\dfrac{1}{98}+\dfrac{1}{97}-\dfrac{1}{96}-\dfrac{1}{95})=0$
Do:
$\dfrac{1}{98}+\dfrac{1}{97}-\dfrac{1}{96}-\dfrac{1}{95}\ne0$
$\to x+100=0$
$\to x= -100$
Vậy $S$={-100}
