Đáp án:
a,
$\frac{-11}{25}$ = $\frac{-10}{25}$ + $\frac{-1}{25}$ = $\frac{-9}{25}$ + $\frac{-2}{25}$
= $\frac{-8}{25}$ + $\frac{-3}{25}$
b,
$\frac{-11}{25}$ = $\frac{10}{25}$ - $\frac{21}{25}$ = $\frac{11}{25}$ - $\frac{22}{25}$
= $\frac{12}{25}$ - $\frac{23}{25}$