Question

\(\dfrac{2}{5}\) + \(\dfrac{5}{4}\) + ( \(\dfrac{-2}{5}\)+ \(\dfrac{5}{4}\)) - \(\dfrac{5}{2}\)

Tính hợp lý

Answer 1

\(=\left(\dfrac{2}{5}+\dfrac{-2}{5}\right)+\left(\dfrac{5}{4}+\dfrac{5}{4}-\dfrac{5}{2}\right)\\ =0+0=0\)

Answer 2

\(\dfrac{2}{5}+\dfrac{5}{4}+\left(\dfrac{-2}{5}+\dfrac{5}{4}\right)-\dfrac{5}{2}\\ =\dfrac{2}{5}+\dfrac{5}{4}-\dfrac{2}{5}+\dfrac{5}{4}-\dfrac{5}{2}\\ =\left(\dfrac{2}{5}-\dfrac{2}{5}\right)+\left(\dfrac{5}{4}+\dfrac{5}{4}\right)-\dfrac{5}{2}\\ =0+\dfrac{10}{4}-\dfrac{5}{2}\\ =\dfrac{5}{2}-\dfrac{5}{2}\\ =0\)

Answer 3

\(\Rightarrow\dfrac{2}{5}+\dfrac{5}{4}+\dfrac{-2}{5}+\dfrac{5}{4}-\dfrac{5}{2}\)

\(\Rightarrow\left(\dfrac{2}{5}-\dfrac{2}{5}\right)+\left(\dfrac{5}{4}+\dfrac{5}{4}\right)-\dfrac{5}{2}\)

\(\Rightarrow\dfrac{10}{4}-\dfrac{5}{2}\)

\(=\dfrac{10-10}{4}=0\)

Answer 4

⇒(25−25)+(54+54)−52⇒(25−25)+(54+54)−52

=10−104=0