5/13x2/7+12/7x5/13-5/13
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a, 3/5 x 7/9 + 11/9 x 3/5 = 3/5 x (7/9 + 11/9) = 3/5 x 2 = 6/5
b, 14/13 : 1/2 + 3/13 x 2 - 2 x 7/13
= 14/13 x 2 + 3/13 x 2 - 2 x 7/13
= 2 x ( 14/13 + 3/13 - 7/13)
= 2 x 10/13 = 20/13
1) = \(\frac{3}{5}\)
2) =\(\frac{6}{7}\)
3)\(\frac{9}{13}\)
4)\(\frac{4}{13}\)
\(\left(19\frac{5}{8}:\frac{7}{12}-13\frac{1}{4}:\frac{7}{12}\right).\frac{4}{5}\)
\(=\left(\frac{157}{8}:\frac{7}{12}-\frac{53}{4}:\frac{7}{12}\right).\frac{4}{5}\)
\(=\left[\left(\frac{157}{8}-\frac{53}{4}\right):\frac{7}{12}\right].\frac{4}{5}\)
\(=\left[\frac{51}{8}:\frac{7}{12}\right].\frac{4}{5}\)
\(=\frac{153}{14}.\frac{4}{5}\)
\(=\frac{306}{35}\)
\(\left(\frac{-2}{5}+\frac{3}{7}\right)-\left(\frac{4}{9}+\frac{12}{20}-\frac{13}{35}\right)+\frac{7}{35}\)
\(=\frac{1}{35}-\frac{212}{315}+\frac{7}{35}\)
\(=\frac{1}{35}+\frac{-212}{315}+\frac{7}{35}\)
\(=\frac{9}{315}+\frac{-212}{315}+\frac{63}{315}\)
\(=\frac{-140}{315}=\frac{-4}{9}\)
`-5/7xx3/13-5/7xx10/13+12/7`
`=-5/7xx(3/13+10/13)+12/7`
`=-5/7xx13/13+12/7=-5/7+12/7=7/7=1`
\(\frac{6}{5}-\frac{1}{4}+\frac{4}{5}-\frac{3}{4}\)
\(=\left(\frac{6}{5}+\frac{4}{5}\right)-\left(\frac{1}{4}+\frac{3}{4}\right)\)
\(=2-1\)
\(=1\)
\(\frac{7}{9}-\frac{5}{12}+\frac{2}{9}-\frac{7}{12}\)
\(=\left(\frac{7}{9}+\frac{2}{9}\right)-\left(\frac{5}{12}+\frac{7}{12}\right)\)
\(=1-1\)
\(=0\)
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
`5/13 xx 2/7 +12/7 xx 5/13 - 5/13`
`= 5/13 xx 2/7 +12/7 xx 5/13 - 5/13xx1`
`= 5/13 xx (2/7 + 12/7 - 1)`
`= 5/13 xx ( 14/7 -1 )`
`= 5/13 xx ( 2-1)`
`= 5/13 xx 1`
`= 5/13`
\(\dfrac{5}{13}x\dfrac{2}{7}+\dfrac{12}{7}x\dfrac{5}{13}-\dfrac{5}{13}=\dfrac{5}{3}x\left(\dfrac{2}{7}+\dfrac{12}{7}-1\right)=\dfrac{5}{3}x\left(2-1\right)=\dfrac{5}{3}\)