Thực hiện phép tính (Tính nhanh nếu có thể) a) -2/15+3/10 b) 9.(-1/3)^2+1/6. căn 4

a) $\frac{-2}{15}+\frac{3}{10}$

$=\frac{-4}{30}+\frac{9}{30}$

$=\frac{5}{30}=\frac{1}{6}$

b) $9.{(-\frac{1}{3})}^2+\frac{1}{6}.\sqrt{4}$

$=9.\frac{1}{9}+\frac{1}{6}.2$

$=1+\frac{1}{3}$

$=\frac{4}{3}$.

c) $15\frac{1}{4}:\frac{5}{7}-25\frac{1}{4}:\frac{5}{7}$

$=(15\frac{1}{4}-25\frac{1}{4}):\frac{5}{7}$

$=-10.\frac{7}{5}$ = −14.