Question

Tính hợp lý giá trị của các biểu thức sau:
\(A=49\dfrac{8}{23}-\left(5\dfrac{7}{32}+14\dfrac{8}{23}\right)\)

\(B=6\dfrac{3}{8}+5\dfrac{1}{2}\)

\(C=\dfrac{-3}{7}\cdot\dfrac{5}{9}+\dfrac{4}{9}\cdot\dfrac{-3}{7}+2\dfrac{3}{7}\)

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

Answer 1

\(A=\dfrac{1135}{23}-\left(\dfrac{167}{32}+\dfrac{330}{23}\right)\)

\(A=\dfrac{1135}{23}-\left(\dfrac{3841}{736}+\dfrac{10560}{736}\right)\)

\(A=\dfrac{1135}{23}-\dfrac{14401}{736}\)

\(A=\dfrac{36320}{736}-\dfrac{14401}{736}\)

\(A=\dfrac{21919}{736}=\dfrac{953}{32}\)

 

\(B=\dfrac{51}{8}+\dfrac{11}{2}\)

\(B=\dfrac{51}{8}+\dfrac{44}{8}\)

\(B=\dfrac{95}{8}\)

 

\(C=\dfrac{-3}{7}.\dfrac{5}{9}+\dfrac{4}{9}.\dfrac{-3}{7}+\dfrac{17}{7}\)

\(C=\dfrac{-3}{7}.\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\dfrac{17}{7}\)

\(C=\dfrac{-3}{7}.1+\dfrac{17}{7}\)

\(C=\dfrac{-3}{7}+\dfrac{17}{7}\)

\(C=\dfrac{14}{7}=2\)

 

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

\(D=\dfrac{58}{7}-\left(\dfrac{217}{63}+\dfrac{270}{63}\right)\)

\(D=\dfrac{58}{7}-\dfrac{487}{63}\)

\(D=\dfrac{522}{63}-\dfrac{487}{63}\)

\(D=\dfrac{35}{65}=\dfrac{5}{9}\)

Answer 2

a:\(=49+\dfrac{8}{23}-5-\dfrac{7}{32}-14-\dfrac{8}{23}\)

\(=30-\dfrac{7}{32}=\dfrac{953}{32}\)

b: \(=6.375+5.5=11.875\)

c: \(=\dfrac{-3}{7}\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+2+\dfrac{3}{7}=2\)

d: \(=8+\dfrac{2}{7}-3-\dfrac{4}{9}-4-\dfrac{2}{7}=1-\dfrac{4}{9}=\dfrac{5}{9}\)