Question

mình cần lời giải chi tiết ạ :((

Answer 1

Câu 3:

a. \(\dfrac{5}{12}+\dfrac{7}{12}\)=\(\dfrac{12}{12}=1\)

b. \(\dfrac{9}{4}-\dfrac{-7}{5}=\dfrac{45}{20}-\dfrac{-28}{20}=\dfrac{73}{20}\)

c.\(\dfrac{-5}{7}+\dfrac{3}{4}+\dfrac{-1}{5}+\dfrac{-2}{5}+\dfrac{1}{4}\)

=\(\left(\dfrac{-5}{7}+\dfrac{-2}{7}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\dfrac{-1}{5}\)

=\(\dfrac{-7}{7}+\dfrac{4}{4}+\dfrac{-1}{5}\)

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

=  0 + \(\dfrac{-1}{5}\)=\(\dfrac{-1}{5}\)

Answer 2

a) 5/12+ 7/12

= 12/12

=1

b) 9/4- (-7/5)

= 9/4+ 7/5

=45/ 20+ 28/ 20

= 73/ 20

Answer 3

 a) \(\dfrac{5}{12}+\dfrac{7}{12}=\dfrac{5+7}{12}=\dfrac{12}{12}=1\)

b) \(\dfrac{9}{4}-\dfrac{-7}{5}=\dfrac{73}{20}\)

c) \(\dfrac{-5}{7}+\dfrac{3}{4}+\dfrac{-1}{5}+\dfrac{-2}{7}+\dfrac{1}{4}\) \(=\left(\dfrac{-5}{7}+\dfrac{-2}{7}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\dfrac{-1}{5}\) \(=\left(-1\right)+1+\dfrac{-1}{5}=\dfrac{-1}{5}\)