Sr, câu 2   2/3   là    1/16

cau 4 kho the

1

a) \(\frac{14}{7}+\frac{5}{9}+\frac{4}{9}-2\)

\(=2\frac{5}{9}+\frac{4}{9}-2\)

\(=3-2=1\)

b) \(\frac{31}{25}+\left(\frac{15}{16}-\frac{6}{15}\right)+\frac{1}{16}\)

\(=\frac{31}{25}+\frac{43}{80}+\frac{1}{16}\)

\(=1\frac{311}{400}+\frac{1}{16}\)

\(=1\frac{21}{25}\)

A = 1/3 - 3/4 + 3/5 + 1/72 -2/9 -1/36 +1 /15

A = (1/3 + 3/5 +1/15 ) - ( 3/4 + 2/9 +1/36 ) +1/72

A = 1 - 1 +1/ 72 = 1/72

Dúng nha **** đi

\(=\dfrac{1}{3}-\dfrac{3}{4}+\dfrac{3}{5}+\dfrac{1}{72}-\dfrac{2}{9}-\dfrac{1}{30}+\dfrac{1}{15}\)

\(=\left(\dfrac{1}{3}+\dfrac{3}{5}+\dfrac{1}{15}\right)+\left(-\dfrac{3}{4}-\dfrac{2}{9}+\dfrac{1}{72}\right)-\dfrac{1}{30}\)

\(=\dfrac{5+9+1}{15}+\dfrac{-54-16+1}{72}-\dfrac{1}{30}\)

\(=\dfrac{29}{30}+\dfrac{-69}{72}=\dfrac{1}{120}\)

\(\frac{1}{3}-\frac{3}{4}-\left(-\frac{3}{5}\right)+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)

\(=\frac{1}{3}-\frac{3}{4}+\frac{3}{5}+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)

\(=\left(\frac{1}{3}-\frac{2}{9}\right)+\left(-\frac{3}{4}-\frac{1}{36}\right)+\left(\frac{3}{5}+\frac{1}{15}\right)+\frac{1}{72}\)

\(=\left(\frac{3}{9}-\frac{2}{9}\right)+\left(-\frac{27}{36}-\frac{1}{36}\right)+\left(\frac{9}{15}+\frac{1}{15}\right)+\frac{1}{72}\)

\(=\frac{1}{9}+\frac{-7}{9}+\frac{2}{3}+\frac{1}{72}\)

\(=-\frac{2}{3}+\frac{2}{3}+\frac{1}{72}\)

\(=0+\frac{1}{72}=\frac{1}{72}\)

Bài làm

       \(\frac{1}{3}+\frac{3}{4}-\left(-\frac{3}{5}\right)+\frac{1}{72}+\frac{2}{9}-\left(-\frac{1}{36}\right)+\frac{1}{15}\)

\(=\frac{1}{3}+\frac{3}{4}+\frac{3}{5}+\frac{1}{72}+\frac{2}{9}+\frac{1}{36}+\frac{1}{15}\)

\(=\left(\frac{1}{3}+\frac{3}{5}+\frac{1}{15}\right)+\left(\frac{1}{36}+\frac{3}{4}\right)+\left(\frac{1}{72}+\frac{2}{9}\right)\)

\(=\left(\frac{5}{15}+\frac{9}{15}+\frac{1}{15}\right)+\left(\frac{1}{36}+\frac{27}{36}\right)+\left(\frac{16}{72}+\frac{1}{72}\right)\)

\(=1+\frac{28}{36}+\frac{18}{72}\)

\(=\frac{36}{36}+\frac{28}{36}+\frac{9}{36}\)

\(=\frac{73}{36}\)

~ Không chắc có đúng hay không nx. ~
# Học tốt #

Sửa đề :

\(\frac{1}{3}+\frac{3}{4}-\left[-\frac{3}{5}\right]+\frac{1}{72}+\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)

\(=\frac{1}{3}+\frac{3}{4}+\frac{3}{5}+\frac{1}{72}+\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)

\(=\left[\frac{1}{3}+\frac{3}{5}+\frac{1}{15}\right]-\left[\frac{3}{4}+\frac{2}{9}+\frac{1}{36}\right]+\frac{1}{72}\)

\(=\left[\frac{5}{15}+\frac{9}{15}+\frac{1}{15}\right]-\left[\frac{27}{36}+\frac{8}{36}+\frac{1}{36}\right]+\frac{1}{72}\)

\(=1-1+\frac{1}{72}=\frac{1}{72}\)