bài 2 ; tính tổng
a. 2/7 +3/7
b. 3/8+5/8
c.1/7+ -4/7
d. 7/-25+-8/25
e. 6/18+-14/21
f. 6/13 +-14/39
g. -3/21 +6/42
h. 7/21+ 9/-36
bài 3 ;
a. 5/3 + ( 7+ -5/3)
b. -7/31 + (24/17 + 7/31)
c. 3/7 + [ -1/5 + -3/7]
bài 4;
a. 6/5 +[ 3+-1/5]
b. -3/5+[ -2/5+2]
c. -3/5 +( -2/5 +2 )
d.-5/11 +[ -6/11 +1]
e. -17/13 + [ 25/ 101 + 4/13]
mình đang cần gấp mn giúp mình vs mình cảm ơn
Bài 3:
\(a.\dfrac{5}{3}+\left(7+\dfrac{-5}{3}\right)\\ =\dfrac{5}{3}+7+\dfrac{-5}{3}\\ =\left(\dfrac{5}{3}-\dfrac{5}{3}\right)+7\\ =7\\ b.\dfrac{-7}{31}+\left(\dfrac{24}{17}+\dfrac{7}{31}\right)\\ =\dfrac{-7}{31}+\dfrac{24}{17}+\dfrac{7}{31}\\ =\left(\dfrac{7}{31}-\dfrac{7}{31}\right)+\dfrac{24}{17}\\ =\dfrac{24}{17}\\ c.\dfrac{3}{7}+\left(\dfrac{-1}{5}+\dfrac{-3}{7}\right)\\ =\dfrac{3}{7}+\dfrac{-1}{5}+\dfrac{-3}{7}\\ =\left(\dfrac{3}{7}-\dfrac{3}{7}\right)+\dfrac{-1}{5}\\ =-\dfrac{1}{5}\)