Đáp án:
$\text{a) 14.}$
$\text{b) $\dfrac{-17}{5}$.}$
Giải thích các bước giải:
$\text{a) $\sqrt{196}$ = $\sqrt{14^2}$ = 14.}$
$\text{b) $\dfrac{1}{3}$.$\sqrt{81}$ - $\dfrac{2}{5}$.$\sqrt{225}$ - $\sqrt{\dfrac{4}{25}}$.}$
$\text{= $\dfrac{1}{3}$.9 - $\dfrac{2}{5}$.15 - $\dfrac{2}{5}$.}$
$\text{= $\dfrac{9}{3}$ - $\dfrac{2}{5}$.(15 + 1).}$
$\text{= $\dfrac{9}{3}$ - $\dfrac{2}{5}$.16.}$
$\text{= 3 - $\dfrac{32}{5}$.}$
$\text{= $\dfrac{15}{5}$ - $\dfrac{32}{5}$.}$
$\text{= $\dfrac{-17}{5}$.}$
