Đáp án:
A= $\dfrac{4}{5}$ - $\dfrac{3}{8}$ - $\dfrac{2}{3}$ + $\dfrac{1}{4}$
= $\dfrac{96}{120}$ - $\dfrac{45}{120}$ - $\dfrac{80}{120}$ + $\dfrac{30}{120}$
= $\dfrac{96-45-8+30}{120}$
= $\dfrac{1}{120}$
B = $\dfrac{1}{2}$ + $\dfrac{3}{5}$- $\dfrac{1}{3}$- $\dfrac{2}{7}$
= $\dfrac{105}{210}$ + $\dfrac{126}{210}$ - $\dfrac{70}{210}$ - $\dfrac{60}{210}$
= $\dfrac{105 + 126 - 70 - 60}{210}$
= $\dfrac{101}{210}$
Giải thích các bước giải:
