Tính nhanh:
A = 1/3 - 3/4 - (-3/5) + 1/72 - 2/9 - 1/36 + 1/15
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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
\(\frac{1}{3}-\frac{3}{4}-\left(-\frac{3}{5}\right)+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)
\(=\frac{1}{3}-\frac{3}{4}+\frac{3}{5}+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)
\(=\left(\frac{1}{3}-\frac{2}{9}\right)+\left(-\frac{3}{4}-\frac{1}{36}\right)+\left(\frac{3}{5}+\frac{1}{15}\right)+\frac{1}{72}\)
\(=\left(\frac{3}{9}-\frac{2}{9}\right)+\left(-\frac{27}{36}-\frac{1}{36}\right)+\left(\frac{9}{15}+\frac{1}{15}\right)+\frac{1}{72}\)
\(=\frac{1}{9}+\frac{-7}{9}+\frac{2}{3}+\frac{1}{72}\)
\(=-\frac{2}{3}+\frac{2}{3}+\frac{1}{72}\)
\(=0+\frac{1}{72}=\frac{1}{72}\)
ta có : (ghi lại đề)
=6+12+18+24+30/3+6+9+12+15
=2*(3/3+6/6+9/9+12/12+15/15)
=2*(1+1+1+1+1)
=2*5=10
chúc main học tốt nhé
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 :
\(\frac{1}{3}+\frac{3}{4}-\left[-\frac{3}{5}\right]+\frac{1}{72}+\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)
\(=\frac{1}{3}+\frac{3}{4}+\frac{3}{5}+\frac{1}{72}+\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)
\(=\left[\frac{1}{3}+\frac{3}{5}+\frac{1}{15}\right]-\left[\frac{3}{4}+\frac{2}{9}+\frac{1}{36}\right]+\frac{1}{72}\)
\(=\left[\frac{5}{15}+\frac{9}{15}+\frac{1}{15}\right]-\left[\frac{27}{36}+\frac{8}{36}+\frac{1}{36}\right]+\frac{1}{72}\)
\(=1-1+\frac{1}{72}=\frac{1}{72}\)
a: Ta có: \(\dfrac{8}{9}-\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{72}\right)\)
\(=\dfrac{8}{9}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{3}-...+\dfrac{1}{8}-\dfrac{1}{9}\right)\)
=0
Ta có :
\(A=\frac{1}{3}-\frac{3}{4}-\left(-\frac{3}{5}\right)+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)
\(\Rightarrow A=\frac{5}{15}-\frac{54}{72}+\frac{9}{15}+\frac{1}{72}-\frac{16}{72}-\frac{1}{72}+\frac{1}{15}\)
\(\Rightarrow A=\left(\frac{5}{15}+\frac{9}{15}+\frac{1}{15}\right)+\left(-\frac{54}{72}+\frac{1}{72}-\frac{16}{72}-\frac{2}{72}\right)\)
\(\Rightarrow A=1-\frac{71}{72}=\frac{1}{72}\)