Question

Tính nhanh 

\(a,\dfrac{-5}{9}+\dfrac{3}{5}-\dfrac{3}{9}+\dfrac{-2}{5}\)

\(b,\dfrac{5}{17}-\dfrac{9}{15}-\dfrac{2}{17}+\dfrac{-2}{5}\)

Answer 1

a) \(\dfrac{-5}{9}+\dfrac{3}{5}-\dfrac{3}{9}+\dfrac{-2}{5}\)

=\(\left(\dfrac{-5}{9}-\dfrac{3}{9}\right)+\left(\dfrac{3}{5}+\dfrac{-2}{5}\right)\)

=\(\dfrac{-8}{9}+\dfrac{1}{5}=-\dfrac{31}{45}\)

b) \(\dfrac{5}{17}-\dfrac{9}{15}-\dfrac{2}{17}+\dfrac{-2}{5}\)

=\(\left(\dfrac{5}{17}-\dfrac{2}{17}\right)-\left(\dfrac{9}{15}+\dfrac{2}{5}\right)\)

=\(\dfrac{3}{17}-1=\dfrac{-14}{17}\)

 

Answer 2

a) (-5/9) + 3/5 - 3/9 + (-2/5)

= (-5/9) - 3/9 + 3/5 + (-2/5)

= (-2/9) + 1/5

= -1/45

b) 5/17 - 9/15 - 2/17 + (-2/5)

= 5/17 - 2/17 - 9/15 + (-2/5)

= 3/17 - 1/5

= -2/85

Chúc bạn học tốt!! ^^

 

Answer 3

a: Ta có: \(-\dfrac{5}{9}+\dfrac{3}{5}-\dfrac{3}{9}+\dfrac{-2}{5}\)

\(=\dfrac{-8}{9}+\dfrac{1}{5}\)

\(=-\dfrac{31}{45}\)

b: Ta có: \(\dfrac{5}{17}-\dfrac{9}{15}-\dfrac{2}{17}+\dfrac{-2}{5}\)

\(=\dfrac{3}{17}-1\)

\(=-\dfrac{14}{17}\)