Question

Tính nhanh :

a) \(\dfrac{-3}{7}+\dfrac{5}{13}+\dfrac{-4}{7}\)

b) \(\dfrac{-5}{21}+\dfrac{-2}{21}+\dfrac{8}{24}\)

Answer 1

a) -3/7 + 5/13 + -4/7 = -3/7 + 4/7 + 5/13 = -1 + 5/13 = -13/13 + 5/13 = -8/13 b) -5/21 + -2/21 + 8/24 = -7/21 + 1/3 = -1/3 + 1/3 = 0

Answer 2

a) \(\dfrac{-3}{7}+\dfrac{5}{13}+\dfrac{-4}{7}\)

\(=\left(\dfrac{-3}{7}+\dfrac{-4}{7}\right)+\dfrac{5}{13}\)

\(=\left(-1\right)+\dfrac{5}{13}\)

\(=\dfrac{-8}{13}\)

b) \(\dfrac{-5}{21}+\dfrac{-2}{21}+\dfrac{8}{24}\)

\(=\left(\dfrac{-5}{21}+\dfrac{-2}{21}\right)+\dfrac{1}{3}\)

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

\(=0\)

Answer 3

Áp dụng tính chất cơ bản của phép cộng phân số:

Answer 4

 a)       

  \(\dfrac{-3}{7}+\dfrac{5}{13}+\dfrac{-4}{7}\)

=(\(\dfrac{-3}{7}+\dfrac{-4}{7}+\dfrac{5}{13}\))

= -1 + \(\dfrac{5}{13}\)

= \(\dfrac{-8}{13}\)

b)\(\dfrac{-5}{21}+\dfrac{-2}{21}+\dfrac{8}{24}\)

= \(\dfrac{-7}{21}+\dfrac{8}{24}\)

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

= 0