Question

tinh cac bieu thuc sau

a)1/2 + -3/8 + 5/9

b) 13/-30+17/45+-7/18

c)-5/19+7/4-(-2/3)+5/6

Answer 1

a: \(\dfrac{1}{2}+\dfrac{-3}{8}+\dfrac{5}{9}\)

\(=\dfrac{36}{72}-\dfrac{27}{72}+\dfrac{40}{72}\)

\(=\dfrac{49}{72}\)

b: \(\dfrac{13}{-30}+\dfrac{17}{45}+\dfrac{-7}{18}\)

\(=\dfrac{-13}{30}+\dfrac{17}{45}+\dfrac{-7}{18}\)

\(=\dfrac{-39+34-35}{90}=\dfrac{-40}{90}=-\dfrac{4}{9}\)

c: \(-\dfrac{5}{19}+\dfrac{7}{4}-\left(-\dfrac{2}{3}\right)+\dfrac{5}{6}\)

\(=-\dfrac{5}{19}+\dfrac{7}{4}+\dfrac{2}{3}+\dfrac{5}{6}\)

\(=\dfrac{-5}{19}+\dfrac{21+8+10}{12}\)

\(=-\dfrac{5}{19}+\dfrac{39}{12}=\dfrac{-5}{19}+\dfrac{13}{4}=\dfrac{227}{76}\)