Question

Câu 1: Thực hiện phép tính bằng cách hợp lí:

a)\(\dfrac{15}{34}\)+\(\dfrac{7}{21}\)+\(\dfrac{19}{34}\)-\(2^{15}_{17}\)+\(\dfrac{2}{3}\)

b) -(2,73.4+2,85)+4.2,73-(2-2,85)

Answer 1

a)= \(\dfrac{15}{34}+\dfrac{1}{3}+\dfrac{19}{34}-\dfrac{49}{17}+\dfrac{2}{3}\)

= \(\left(\dfrac{15}{34}+\dfrac{19}{34}\right)+\left(\dfrac{1}{3}+\dfrac{2}{3}\right)\)\(-\dfrac{49}{17}\)

= 1 + 1 \(-\dfrac{49}{17}\)

= \(2+\dfrac{49}{17}=\dfrac{34}{17}+\dfrac{49}{17}=\dfrac{83}{17}\)

b) = -(10,92 + 2,85) + 10,92 - ( 2 - 2,85)

= (-10,92 +10,92) + ( 2,85 - 2,85 ) - 2

= 0 + 0 - 2

= -2