Question

Tính giá trị biểu thức bằng cách hợp lý:

A=(\(\left(5-\dfrac{3}{4}+\dfrac{1}{5}\right)-\left(6+\dfrac{7}{4}-\dfrac{8}{5}\right)-\left(2-\dfrac{5}{4}+\dfrac{16}{5}\right)\)

Answer 1

\(A=\left(5-\dfrac{3}{4}+\dfrac{1}{5}\right)-\left(6+\dfrac{7}{4}-\dfrac{8}{5}\right)-\left(2-\dfrac{5}{4}+\dfrac{16}{5}\right)\)

\(A=5-\dfrac{3}{4}+\dfrac{1}{5}-6-\dfrac{7}{4}+\dfrac{8}{5}-2+\dfrac{5}{4}-\dfrac{16}{5}\)

\(A=\left(5-6-2\right)\)\(-\left(\dfrac{3}{4}+\dfrac{7}{4}-\dfrac{5}{4}\right)\)\(+\left(\dfrac{1}{5}+\dfrac{8}{5}-\dfrac{16}{5}\right)\)

\(A=-3\)\(-\dfrac{5}{4}\)\(+\dfrac{-7}{5}\)

\(A=\dfrac{-113}{20}\)

Answer 2

\(A=\left(5-\dfrac{3}{4}+\dfrac{1}{5}\right)-\left(6+\dfrac{7}{4}-\dfrac{8}{5}\right)-\left(2-\dfrac{5}{4}+\dfrac{16}{5}\right)\)

\(A=5-\dfrac{3}{4}+\dfrac{1}{5}-6-\dfrac{7}{4}+\dfrac{8}{5}-2+\dfrac{5}{4}-\dfrac{16}{5}\)

\(A=-3-\dfrac{5}{4}+\dfrac{-7}{5}\)

\(A=-\dfrac{113}{20}\)

Answer 3

Ta có: A = \(\left(5-\dfrac{3}{4}+\dfrac{1}{5}\right)-\left(6+\dfrac{7}{4}-\dfrac{8}{5}\right)-\left(2-\dfrac{5}{4}+\dfrac{16}{5}\right)\)

= \(5-\dfrac{3}{4}+\dfrac{1}{5}-6-\dfrac{7}{4}+\dfrac{8}{5}-2+\dfrac{5}{4}-\dfrac{16}{5}\)

= (5 - 6 - 2) + (- 3/4 - 7/4 + 5/4) + (1/5 + 8/5 - 16/5)

= -3 -5/4 - 19/8

= - 53/8