Câu 13. Tính:
a) \(\frac{5}{7} . \frac{5}{11} + \frac{5}{7} . \frac{6}{11} - \frac{5}{7} . \frac{4}{11}\);
b) \(1 , 2 - 3^{2} + 7 , 5\) \(:\) \(3\).
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\(\frac{5}{7}.\frac{5}{11}+\frac{5}{7}.\frac{2}{11}-\frac{5}{7}.\frac{14}{11}\)
\(=\frac{5}{7}.\left(\frac{5}{11}+\frac{2}{11}-\frac{14}{11}\right)\)
\(=\frac{5}{7}.\frac{-7}{11}\)
\(=\frac{-5}{11}\)
5/7.5/11+5/7.2/11-5/7.14/11
= 5/7.(5/11+2/11-14/11)
=5/7.-7/11
=-5/11
4/7 * 5/11 + 4/7 * 6/11+ (-2/3) = 4/7 * (5/11 + 6/11) + (-2/3)
= 4/7 *1 + (-2/3)
= 4/7 + (-2/3)
= -2/21
\(\frac{4}{7}.\frac{5}{11}+\frac{4}{7}.\frac{6}{11}+\frac{-2}{3}\)
=\(\frac{4}{7}.\left(\frac{5+6}{11}\right)+\frac{-2}{3}\)
=\(\frac{4}{7}.1+\frac{-2}{3}\)
=\(\frac{4}{7}+\frac{-2}{3}\)
=\(\frac{-2}{21}\)
CHÚC BẠN HỌC TỐT
\(\dfrac{2}{7}-\dfrac{3}{11}+\dfrac{5}{7}-\dfrac{8}{11}\\ =\left(\dfrac{2}{7}+\dfrac{5}{7}\right)-\left(\dfrac{3}{11}+\dfrac{8}{11}\right)\\ =\dfrac{7}{7}-\dfrac{11}{11}\\ =1-1\\ =0\)
\(\dfrac{38}{11}+\left(\dfrac{16}{13}+\dfrac{6}{11}\right)\\ =\dfrac{38}{11}+\dfrac{16}{13}+\dfrac{6}{11}\\ =\left(\dfrac{38}{11}+\dfrac{6}{11}\right)+\dfrac{16}{13}\\ =\dfrac{44}{11}+\dfrac{16}{13}\\ =4+\dfrac{16}{13}\\ =\dfrac{52}{13}+\dfrac{16}{13}\\ =\dfrac{68}{13}\\ \dfrac{3}{4}:\dfrac{3}{5}-\dfrac{1}{5}\\ =\dfrac{3}{4}\times\dfrac{5}{3}-\dfrac{1}{5}\\ =\dfrac{5}{4}-\dfrac{1}{5}\\ =\dfrac{25-4}{20}\\ =\dfrac{21}{20}\)
Phép tính 1:
\(\dfrac{38}{11}+\left(\dfrac{16}{13}+\dfrac{6}{11}\right)\)
\(=\left(\dfrac{38}{11}+\dfrac{6}{11}\right)+\dfrac{16}{13}\)
\(=4+\dfrac{16}{13}=\dfrac{4\cdot13+16}{13}\)(Dấu "." trong phép tính là dấu nhân)
\(=\dfrac{68}{13}\)
Phép tính 2:
\(\dfrac{3}{4}:\dfrac{3}{5}-\dfrac{1}{5}\)
\(=\dfrac{3}{4}\cdot\dfrac{5}{3}-\dfrac{1}{5}\)
\(=\dfrac{\left(3\cdot5\right):3\cdot5}{\left(4\cdot3\right):3\cdot5}-\dfrac{1\cdot4}{5\cdot4}\)
\(=\dfrac{25}{20}-\dfrac{4}{20}\)
\(=\dfrac{21}{20}\)
\(\frac{5}{7}.\frac{5}{11}+\frac{5}{7}.\frac{2}{11}+\frac{5}{11}.\frac{14}{7}=\left(\frac{5}{7}.\frac{5}{11}\right)+\left(\frac{5}{7}.\frac{2}{11}\right)+\left(\frac{5}{11}.\frac{14}{7}\right)=\frac{25}{77}+\frac{10}{77}+\frac{10}{11}=\frac{5}{11}+\frac{10}{11}=\frac{15}{11}\)
\(-\frac{5}{7}.\frac{68}{11}+\frac{-5}{7}.\frac{86}{11}+\frac{12}{7}\\ =-\frac{5}{7}.\left(\frac{68}{11}+\frac{86}{11}\right)+\frac{12}{7}\\ =-\frac{5}{7}.\frac{154}{11}+\frac{12}{7}\\ =-\frac{5}{7}.14+\frac{12}{7}\)
\(=-10+\frac{12}{7}\\ =-\frac{70}{10}+\frac{12}{7}=-\frac{58}{7}\)
-5/7.68/11+-5/7.86/11+12/7
=-5/7.(68/11-86/11)+12/7
=-5/7.-18/11+12/7
=90/77+12/7
=90/77+132/77
=222/77
\(\dfrac{1}{3}-\dfrac{3}{5}+\dfrac{5}{7}-\dfrac{7}{9}+\dfrac{9}{11}-\dfrac{11}{13}+\dfrac{13}{15}+\dfrac{11}{13}-\dfrac{9}{11}+\dfrac{7}{9}-\dfrac{5}{7}+\dfrac{3}{5}-\dfrac{1}{3}\)
\(=\left(\dfrac{1}{3}-\dfrac{1}{3}\right)-\left(\dfrac{3}{5}-\dfrac{3}{5}\right)+\left(\dfrac{5}{7}-\dfrac{5}{7}\right)-\left(\dfrac{7}{9}-\dfrac{7}{9}\right)+\left(\dfrac{9}{11}-\dfrac{9}{11}\right)-\left(\dfrac{11}{13}-\dfrac{11}{13}\right)+\dfrac{13}{15}\)
\(=\dfrac{13}{15}\)
31−53+75−97+119−1311+1513+1311−119+97−75+53−31
=(13−13)−(35−35)+(57−57)−(79−79)+(911−911)−(1113−1113)+1315=(31−31)−(53−53)+(75
\(#N\)
\(-\dfrac{11}{7}+\dfrac{13}{-2}+-\dfrac{6}{17}=-\dfrac{113}{14}+-\dfrac{6}{17}=-\dfrac{2005}{238}\)
\(\dfrac{13}{-8}+-\dfrac{7}{20}+\dfrac{3}{-8}=\left(-\dfrac{13}{8}+-\dfrac{3}{8}\right)+-\dfrac{7}{20}=-2+-\dfrac{7}{20}=-\dfrac{47}{20}\)
\(-\dfrac{4}{7}+\dfrac{11}{5}+\dfrac{1}{5}+-\dfrac{7}{3}=-\dfrac{4}{7}+\left(\dfrac{11}{5}+\dfrac{1}{5}\right)+-\dfrac{7}{3}=-\dfrac{4}{7}+\dfrac{12}{5}+-\dfrac{7}{3}=-\dfrac{53}{105}\)
-5/ 12. (2/11+ 9/11+ (-1)
=-5/ 12. [(11/11+(-1)]
=-5/ 12. (1-1)
= -5/12. 0
=0
\(=\dfrac{7}{11}\left(\dfrac{5}{13}+\dfrac{8}{13}\right)-3-\dfrac{7}{11}=-3\)
a) \(\frac57.\frac{5}{11}+\frac57.\frac{6}{11}-\frac57.\frac{4}{11}\)
\(=\frac57.\left(\frac{5}{11}+\frac{6}{11}-\frac{4}{11}\right)\)
\(=\frac57.\frac{7}{11}\)
\(=\frac{5}{11}\)
b) \(1,2-3^2+7,5:3\)
\(=1,2-9+2,5\)
\(=-7,8+2,5\)
\(=-5,3\)