Question

[Trâm Nguyễn]

Tính hợp lí nếu có thể:
a) 1\(\dfrac{2}{5}\)+2\(\dfrac{3}{4}\)-4\(\dfrac{2}{5}\)

b) \(\dfrac{-2}{3}\)+\(\dfrac{4}{15}\)+\(\dfrac{1}{6}\)+\(\dfrac{4}{-9}\)+\(\dfrac{11}{15}\)

SOS EMMM 

Answer 1

[Nguyễn Lê Phước Thịnh]

a: \(1\dfrac{2}{5}+2\dfrac{3}{4}-4\dfrac{2}{5}\)

\(=1,4+2,75-4,4\)

\(=2,75-3=-0,25=-\dfrac{1}{4}\)

b: \(\dfrac{-2}{3}+\dfrac{4}{15}+\dfrac{1}{6}+\dfrac{4}{-9}+\dfrac{11}{15}\)

\(=\left(-\dfrac{2}{3}+\dfrac{1}{6}-\dfrac{4}{9}\right)+\left(\dfrac{4}{15}+\dfrac{11}{15}\right)\)

\(=1+\dfrac{-12+2-8}{18}\)

\(=1+\dfrac{-18}{18}\)

=1-1

=0