√14-6√5 -√21-8√5
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KN
10 tháng 2 2019
\(\frac{7}{8}\div\left(\frac{14}{3}+\frac{14}{4}\right)+\frac{10}{14}\)
\(=\frac{7}{8}\div\left(\frac{56}{12}+\frac{52}{12}\right)+\frac{10}{14}\)
\(=\frac{7}{8}\div\frac{108}{12}+\frac{10}{14}\)
\(=\frac{7}{8}\div9+\frac{5}{7}\)
\(=\frac{7}{8}\times\frac{1}{9}+\frac{5}{7}\)
\(=\frac{7}{72}+\frac{5}{7}\)
\(=\frac{49}{504}+\frac{360}{504}\)
\(=\frac{409}{504}\)
\(\frac{30}{42}\div\left(\frac{5}{7}-\frac{5}{21}\right)+\frac{6}{8}\)
\(=\frac{6}{7}\div\left(\frac{15}{21}-\frac{5}{21}\right)+\frac{3}{4}\)
\(=\frac{6}{7}\div\frac{10}{21}+\frac{3}{4}\)
\(=\frac{6}{7}\times\frac{21}{10}+\frac{3}{4}\)
\(=\frac{126}{70}+\frac{3}{4}\)
\(=\frac{504}{280}+\frac{210}{280}\)
\(=\frac{714}{280}\)
KN
10 tháng 2 2019
\(\left(6-\frac{14}{15}\right).\frac{50}{38}-\frac{8}{18}\)
\(=\left(\frac{90}{15}-\frac{14}{15}\right).\frac{25}{19}-\frac{4}{9}\)
\(=\frac{76}{15}.\frac{25}{19}-\frac{4}{9}\)
\(=\frac{76.25}{15.19}-\frac{4}{9}\)
\(=\frac{19.2.2.5.5}{3.5.19}-\frac{4}{9}\)
\(=\frac{20}{3}-\frac{4}{9}\)
\(=\frac{60}{9}-\frac{4}{9}\)
\(=\frac{56}{9}\)
\(\frac{4}{6}+\frac{5}{21}.\left(\frac{4}{5}-\frac{2}{6}\right)\)
\(=\frac{2}{3}+\frac{5}{21}.\left(\frac{24}{30}-\frac{10}{30}\right)\)
\(=\frac{2}{3}+\frac{5}{21}.\frac{14}{30}\)
\(=\frac{2}{3}+\frac{70}{630}\)
\(=\frac{420}{630}+\frac{70}{630}\)
\(=\frac{490}{630}\)
\(=\frac{7}{9}\)
TN
21 tháng 8 2018
\(\left(6-\frac{4}{15}\right).\frac{25}{8}-\frac{18}{5}:\frac{1}{4}\)
\(=\frac{86}{15}.\frac{25}{8}-\frac{72}{5}\)
\(=\frac{215}{12}-\frac{72}{5}\)
\(=\frac{211}{60}\)
\(\frac{5}{6}:7:\frac{20}{11}+\frac{5}{6}:7:\frac{20}{11}\)
\(=\frac{11}{168}+\frac{11}{168}\)
\(=\frac{11}{84}\)
học tốt
20 tháng 7 2023
`@` `\text {Ans}`
`\downarrow`
`1,`
`a)`
`-7/25 + (-8)/25`
`= (-7 - 8)/25`
`= -15/25`
`= -3/5`
`b)`
`6/13 + (-15)/39`
`= 18/39 + (-15)/39`
`= (18 - 15)/39`
`= 3/39`
`= 1/13`
`c)`
`5/7 + 4/(-14)`
`= 10/14 + (-4)/14`
`= (10 - 4)/14`
`= 6/14`
`= 3/7`
`d)`
`-8/18 + (-15)/27`
`= -4/9 + (-5)/9`
`= (-4-5)/9`
`= -9/9 = -1`
NN
20 tháng 7 2023
`2,`
`a)`
`3/5 + (-7)/4`
`= 12/20 + (-35)/20`
`= (12 - 35)/20`
`=-23/20`
`b)`
`(-2) + (-5)/8`
`= (-16)/8 + (-5)/8`
`= (-16 - 5)/8`
`= -21/8`
`c)`
`1/8 + (-5)/9`
`= 9/72 + (-40)/72`
`= (9-40)/72`
`= -31/72`
`d)`
`6/13 + (-14)/39`
`= 18/39 + (-14)/39`
`= (18 - 14)/39`
`= 4/39`
`e)`
`(-18)/24 + 15/21`
`= (-3)/4 + 5/7`
`= (-21)/28 + 20/28`
`= (-21 + 20)/28`
`= -1/28`
20 tháng 7 2023
1)1/6 - - 5/6 = 1/6 + 5/6 = 1
2)6/13 - -14/39 = 6/13 + 14/39= 32/39
3)4/5 - 4/-18 = 4/5 + 4/18= 46/45
4)7/21 - 9/-36 = 7/21 + 9/36 = 7/12
5)-12/18 - -21/35 = -12/18 + 21/35 = -1/15
6)-3/21 - 6/42 = -2/7
7)-18/24 - 15/21 = -41/28
8)1/6 - 2/5 =-7/30
13 tháng 3 2023
7/8*4/21=7/21*4/8=1/3*1/2=1/6
5/14*6=30/14=15/7
=>Đề sai rồi bạn
LD
2
17 tháng 2 2022
a) 5/-6 < 5/-7 b) -12/15 < 1/5 c) -3/8 > -5/6 d) -14/21 < 60/-72
PT
1
\(\sqrt{14}-6\sqrt{5}-\sqrt{21}-8\sqrt{5}.\)
\(=\left(-6\sqrt{5}-8\sqrt{5}\right)+\left(\sqrt{14}-\sqrt{21}\right)\)
\(=-14\sqrt{5}+\sqrt{7}\left(\sqrt{2}-\sqrt{3}\right)\)