Tính hợp lí -2/5 × 4/7 + -3/5 × 2/7 + -3/5
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\(#N\)
\(-\dfrac{11}{7}+\dfrac{13}{-2}+-\dfrac{6}{17}=-\dfrac{113}{14}+-\dfrac{6}{17}=-\dfrac{2005}{238}\)
\(\dfrac{13}{-8}+-\dfrac{7}{20}+\dfrac{3}{-8}=\left(-\dfrac{13}{8}+-\dfrac{3}{8}\right)+-\dfrac{7}{20}=-2+-\dfrac{7}{20}=-\dfrac{47}{20}\)
\(-\dfrac{4}{7}+\dfrac{11}{5}+\dfrac{1}{5}+-\dfrac{7}{3}=-\dfrac{4}{7}+\left(\dfrac{11}{5}+\dfrac{1}{5}\right)+-\dfrac{7}{3}=-\dfrac{4}{7}+\dfrac{12}{5}+-\dfrac{7}{3}=-\dfrac{53}{105}\)
1/2 + 2/3 - 3/4 * 4/5 * 5/6 * 6/7 * 7/8 * 8/9 *...* 29/30 : 6/10
= 1/2 + 2/3 - 1/10 : 6/10
= 1/2 + 2/3 - 1/6
= 1
\(\left(3-\frac{1}{4}+\frac{2}{3}\right)-\left(5-\frac{1}{3}-\frac{6}{5}\right)-\left(6-\frac{7}{4}+\frac{3}{2}\right)\)
\(=3-\frac{1}{4}+\frac{2}{3}-5+\frac{1}{3}+\frac{6}{5}-6+\frac{7}{4}-\frac{3}{2}\)
\(=\left(3-5-6\right)+\left(\frac{-1}{4}+\frac{7}{4}\right)+\left(\frac{2}{3}+\frac{1}{3}\right)+\left(\frac{6}{5}-\frac{3}{2}\right)\)
\(=\left(-8\right)+2+1+\frac{-3}{10}\)
\(=\left(-5\right)+\frac{-3}{10}=\frac{-53}{10}=-5,3\)
(3-1/4+2/3)-(5-1/3-6/5)-(6-7/4+3/2)
=3-1/4+2/3-5-1/3-6/5-6-7/4+3/2
=(3-5-6)+(-1/4-7/4)+(2/3-1/3)+(6/5/3/2
=(-8)+2+1+(-3/10)
=(-5)+(-3/10)=-53/10=-5,3
a: =(-20/23-3/23)+(2/3+2/5+7/15)
=-1+10/15+6/15+7/15
=23/15-1=8/15
b: \(=\dfrac{7}{5}\cdot\dfrac{29}{4}-\dfrac{7}{5}\cdot\dfrac{9}{4}+\dfrac{41}{13}=\dfrac{7}{5}\cdot5+\dfrac{41}{13}=7+\dfrac{41}{13}=\dfrac{132}{13}\)
c: =3,07+7,005-23,005+5,23
=8,3-16
=-7,7
\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{-3}{5}.\dfrac{2}{7}+\dfrac{-3}{5}\)
= \(\dfrac{-8}{35}+\dfrac{-6}{35}+\dfrac{-3}{5}\)
=\(\dfrac{-8-6-21}{35}\)
=\(\dfrac{-35}{35}\)
=-1
`(-2)/5.4/7+(-3)/5.2/7+(-3)/5`
`=(-8)/3 +(-6)/35+(-3)/5`
`=(-8)-6-21/35`
`=(-35)/35`
`=(-1)`
`@Nae`