Đáp án:
A 8$\dfrac{2}{7}$ - ( 3$\dfrac{4}{9}$ + 4$\dfrac{2}{7}$)
Cách 1 : $\dfrac{58}{7}$ - ( $\dfrac{31}{9}$ + $\dfrac{30}{7}$)
= $\dfrac{58}{7}$ - $\dfrac{487}{63}$
= $\dfrac{522}{63}$ - $\dfrac{487}{63}$
= $\dfrac{5}{9}$
Cách 2 : $\dfrac{58}{7}$ - $\dfrac{30}{7}$ -$\dfrac{31}{9}$
= 4 - $\dfrac{31}{9}$
= $\dfrac{5}{9}$
B Cách 1 : (10$\dfrac{2}{9}$ + 2$\dfrac{3}{5}$) - 6$\dfrac{2}{9}$
= ( $\dfrac{92}{9}$ + $\dfrac{13}{5}$ ) - $\dfrac{56}{9}$
= $\dfrac{343}{45}$ - $\dfrac{56}{9}$
= $\dfrac{343}{45}$ - $\dfrac{280}{45}$
= $\dfrac{7}{5}$
Cách 2 :
$\dfrac{92}{9}$ - $\dfrac{56}{9}$ - $\dfrac{13}{5}$
= 4 - $\dfrac{13}{5}$
= $\dfrac{7}{5}$
Giải thích các bước giải:
