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1) = \(\frac{3}{5}\)
2) =\(\frac{6}{7}\)
3)\(\frac{9}{13}\)
4)\(\frac{4}{13}\)
1; = ( -4/10 + 3/10 ) : ( -2/5 + 2/3 ) = -1/10 : ( -6/15 + 10/15 ) = -1/10 : 4/15 = -1/10 . 15/4 = -15/40 = -3/8
2; = 25/2 . -5/7 + 39/4 + -3/2 . 5/7 = -125/14 + 39/4 + -15/14 = ( -125/14 + -15/14 ) + 39/4 = -10 + 39/4 = -40/4 + 39/4 = -1/4
3; = 5/52 + 35/52 + 40/52 = 40/52 + 40/52 = 80/52 = 20/13
4; = ( -39/52 + 20/52 ) . 7/2 - ( 117/52 + 32/52 ) . 7/2 = -19/52 . 7/2 - 149/52 . 7/2 = ( -19/52 + -149/52 ) . 7/2 = -168/52 .7/2 = -147/13
5; = ( 36/12 + -9/12 + 8/12 ) - ( -12/6 + -8/6 + -9/6 ) - ( 6/6 - 14/6 - 27/6 ) = 35/12 + 10/12 + 70/12 = 115/12
6; = -1/3 + -8/35 +-2/9 + -1/135 +4/5 +-4/9 +3/7 = (-1/3 + -2/9 + -4/9 ) + ( -8/35 + 4/5 + 3/7 ) + -1/135 = ( -1/3 + -2/3 ) + ( -8/35 + 28/35 + 15/35 ) + -1/135 = -1 + 1 + -1/135 = -1/135
1) Ta có: \(\frac{-4}{7}-\frac{11}{19}+\frac{13}{19}\cdot\frac{-3}{7}+\frac{2}{19}:\frac{-7}{4}\)
\(=\frac{-4}{7}-\frac{11}{19}-\frac{39}{133}-\frac{8}{133}\)
\(=\frac{-76}{133}-\frac{77}{133}-\frac{39}{133}-\frac{8}{133}\)
\(=\frac{-200}{133}\)
2) Ta có: \(\left(\frac{-4}{9}+\frac{3}{5}\right):\frac{1}{\frac{1}{5}}+\left(\frac{1}{5}-\frac{5}{9}\right):\frac{1}{\frac{1}{5}}\)
\(=\left(\frac{-4}{9}+\frac{3}{5}\right)\cdot\frac{1}{5}+\left(\frac{1}{5}-\frac{5}{9}\right)\cdot\frac{1}{5}\)
\(=\frac{1}{5}\left(\frac{-4}{9}+\frac{3}{5}+\frac{1}{5}-\frac{5}{9}\right)\)
\(=\frac{1}{5}\left(-1+\frac{4}{5}\right)\)
\(=\frac{1}{5}\cdot\frac{-1}{5}=\frac{-1}{25}\)
3) Ta có: \(\frac{4}{5}-\left(-\frac{2}{7}\right)-\frac{7}{10}\)
\(=\frac{4}{5}+\frac{2}{7}-\frac{7}{10}\)
\(=\frac{56}{70}+\frac{20}{70}-\frac{49}{70}\)
\(=\frac{27}{70}\)
4) Ta có: \(\frac{2}{7}-\left(-\frac{13}{15}+\frac{4}{9}\right)-\left(\frac{5}{9}-\frac{2}{15}\right)\)
\(=\frac{2}{7}+\frac{13}{15}-\frac{4}{9}-\frac{5}{9}+\frac{2}{15}\)
\(=\frac{2}{7}+1-1=\frac{2}{7}\)
\(\frac{6}{5}-\frac{1}{4}+\frac{4}{5}-\frac{3}{4}\)
\(=\left(\frac{6}{5}+\frac{4}{5}\right)-\left(\frac{1}{4}+\frac{3}{4}\right)\)
\(=2-1\)
\(=1\)
\(\frac{7}{9}-\frac{5}{12}+\frac{2}{9}-\frac{7}{12}\)
\(=\left(\frac{7}{9}+\frac{2}{9}\right)-\left(\frac{5}{12}+\frac{7}{12}\right)\)
\(=1-1\)
\(=0\)
các câu sau tương tự
A=1
B=0
C=ÂM 8/15
D=0
E=2
F=3/2
H=2/3
LẦN SAU CHO KHÓ SÍU NHA LỚP 5 CŨNG LÀM ĐC
Sửa đề :\(1,-\dfrac{5}{9}\times\dfrac{2}{13}+-\dfrac{5}{13}\times\dfrac{11}{9}-\dfrac{4}{9}\)
\(=-\dfrac{5}{9}\times\dfrac{2}{13}+-\dfrac{5}{9}\times\dfrac{11}{13}-\dfrac{4}{9}\)
\(=-\dfrac{5}{9}\times\left(\dfrac{2}{13}+\dfrac{11}{13}\right)-\dfrac{4}{9}\)
\(=-\dfrac{5}{9}\times1-\dfrac{4}{9}\)
\(=-1\)
\(2,\dfrac{4}{9}\times\left(\dfrac{5}{7}+\dfrac{2}{5}\right)-\dfrac{4}{9}\times\left(-\dfrac{2}{7}+\dfrac{7}{5}\right)\)
\(=\dfrac{4}{9}\times\left[\left(\dfrac{5}{7}+\dfrac{2}{5}\right)-\left(-\dfrac{2}{7}+\dfrac{7}{5}\right)\right]\)
\(=\dfrac{4}{9}\times\left[\dfrac{5}{7}+\dfrac{2}{5}+\dfrac{2}{7}-\dfrac{7}{5}\right]\)
\(=\dfrac{4}{9}\times\left[\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\left(\dfrac{2}{5}-\dfrac{7}{5}\right)\right]\)
\(=\dfrac{4}{9}\times\left[1+-1\right]\)
\(=\dfrac{4}{9}\times0=0\)
\(3,\left(\dfrac{5}{4}+\dfrac{3}{4}\right)\times\dfrac{4}{7}+\left(\dfrac{3}{4}+\dfrac{9}{4}\right)\times\dfrac{4}{7}\)
\(=\left[\left(\dfrac{5}{4}+\dfrac{3}{4}\right)+\left(\dfrac{3}{4}+\dfrac{9}{4}\right)\right]\times\dfrac{4}{7}\)
\(=\left[\dfrac{5}{4}+\dfrac{3}{4}+\dfrac{3}{4}+\dfrac{9}{4}\right]\times\dfrac{4}{7}\)
\(=\left[\left(\dfrac{5}{4}+\dfrac{9}{4}\right)+\left(\dfrac{3}{4}+\dfrac{3}{4}\right)\right]\times\dfrac{4}{7}\)
\(=\left[\dfrac{7}{2}+\dfrac{3}{2}\right]\times\dfrac{4}{7}\)
\(=5\times\dfrac{4}{7}\)
\(=\dfrac{20}{7}\)
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