Question

Tính hợp lý:

C = 3/7 × 5/9 + 4/9 × 3/7 - 3/7

D= 8 và 2 phần 7 - ( 3 và 4 phần 9 + 4 và 2 phần 7)

Ghi cả lời nhw

 

Answer 1

\(C=\dfrac{3}{7}\times\dfrac{5}{9}+\dfrac{4}{9}\times\dfrac{3}{7}-\dfrac{3}{7}\)

\(=\dfrac{3}{7}\times\dfrac{5}{9}+\dfrac{4}{9}\times\dfrac{3}{7}-\dfrac{3}{7}\times1\)

\(=\dfrac{3}{7}\times\left(\dfrac{5}{9}+\dfrac{4}{9}-1\right)\)

\(=\dfrac{3}{7}\times0=0\)

\(D=8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)

\(=\dfrac{58}{7}-\left(\dfrac{31}{9}+\dfrac{30}{7}\right)\)

\(=\dfrac{58}{7}-\dfrac{31}{9}-\dfrac{30}{7}\)

\(=\left(\dfrac{58}{7}-\dfrac{30}{7}\right)-\dfrac{31}{9}\)

\(=4-\dfrac{31}{9}=\dfrac{36}{9}-\dfrac{31}{9}\)

\(=\dfrac{5}{9}\)