( $\dfrac{17}{28}$ + $\dfrac{18}{29}$ - $\dfrac{19}{30}$ - $\dfrac{20}{31}$ ) $\times$ ( $\dfrac{-5}{12}$ + $\dfrac{1}{4}$ + $\dfrac{1}{6}$ )
= ( $\dfrac{17}{28}$ + $\dfrac{18}{29}$ - $\dfrac{19}{30}$ - $\dfrac{20}{31}$ ) $\times$ ( $\dfrac{-5}{12}$ + $\dfrac{3}{12}$ + $\dfrac{2}{12}$ )
= ( $\dfrac{17}{28}$ + $\dfrac{18}{29}$ - $\dfrac{19}{30}$ - $\dfrac{20}{31}$ ) $\times$ $\dfrac{0}{12}$
= ( $\dfrac{17}{28}$ + $\dfrac{18}{29}$ - $\dfrac{19}{30}$ - $\dfrac{20}{31}$ ) $\times$ 0
= 0
Xin hay nhất chúc học tốt ( thử latex )
