Tính nhanh \(\frac{9}{13}+\frac{9}{13}+\frac{9}{13}+\frac{9}{13}\times3+\frac{9}{13}\times7\)
K
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24 tháng 7 2017
= 1/3 - 1/3 + 5/7 - 5/7 - 7/9 + 7/9 +9/11 - 9/11 -11/13 + 11/13 +13/15
= 0 + 0 - 0 + 0 -0 + 13/15
= 0 + 13/15
= 13/15
24 tháng 7 2017
\(\frac{1}{3}-\frac{3}{5}+\frac{5}{7}-\frac{7}{9}+\frac{9}{11}-\frac{11}{13}+\frac{13}{15}+\frac{11}{13}-\frac{9}{11}+\frac{7}{9}-\frac{5}{7}+\frac{3}{5}-\frac{1}{3}\)
\(=\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{3}{5}-\frac{3}{5}\right)+\left(\frac{5}{7}-\frac{5}{7}\right)+\left(\frac{7}{9}-\frac{7}{9}\right)+\left(\frac{9}{11}-\frac{9}{11}\right)+\left(\frac{11}{13}-\frac{11}{13}\right)+\frac{13}{15}\)
\(=0+0+0+0+0+0+\frac{13}{15}\)
\(=\frac{13}{15}\)
TD
10 tháng 3 2018
\(P=\frac{6}{7}.\frac{8}{13}+\frac{6}{9}.\frac{9}{7}-\frac{3}{13}.\frac{6}{7}\)
\(P=\frac{6}{7}.\frac{8}{13}+\frac{6}{7}-\frac{3}{13}.\frac{6}{7}\)
\(P=\frac{6}{7}.\left(\frac{8}{13}+1-\frac{3}{13}\right)\)
\(P=\frac{6}{7}.\frac{18}{13}\)
\(P=\frac{108}{91}\)
HN
10 tháng 3 2018
\(\frac{6}{7}.\frac{8}{13}+\frac{6}{9}.\frac{9}{7}-\frac{3}{13}.\frac{6}{7}\)
= \(\frac{6}{7}.\left(\frac{8}{13}-\frac{3}{13}\right)+\frac{6}{9}.\frac{9}{7}\)
= \(\frac{6}{7}.\frac{5}{13}+\frac{54}{63}\)
= \(\frac{30}{91}+\frac{54}{63}\)
= \(\frac{30}{91}+\frac{6}{7}\)
= \(\frac{30}{91}+\frac{78}{91}\)
= \(\frac{108}{91}\)
PT
5
DN
21 tháng 8 2017
B=\(\frac{5}{9}\)x{\(\frac{7}{13}\)+\(\frac{9}{13}\)-\(\frac{3}{13}\)}
B=\(\frac{5}{9}\)x 1
B=\(\frac{5}{9}\)
Vậy B=\(\frac{5}{9}\)
Chúc bạn hok tốt
D
19 tháng 8 2016
\(=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(\frac{3}{7}-\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(\frac{2}{11}-\frac{2}{11}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)+\frac{9}{16}\)
= 0 + \(\frac{9}{16}\)
= \(\frac{9}{16}\)
tick nha bn
19 tháng 8 2016
\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)
\(=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(-\frac{3}{7}+\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(-\frac{2}{11}+\frac{2}{11}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)-\frac{9}{16}\)
\(=0+0+0+0+0-\frac{9}{16}\)
\(=-\frac{9}{16}\)
^...^ 
^_^
23 tháng 6 2016
B=(1/5-1/5) + (-3/7+3/7) + (5/9-5/9) + (-2/11+2/11) + (7/13-7/13) - 9/16
= 0 + 0 + 0 + 0 + 0 - 9/16
=-9/16
NT
3
25 tháng 4 2018
\(\frac{5}{9}-\frac{7}{13}-\frac{5}{9}.\frac{3}{13}+\frac{-5}{9}.\frac{6}{9}\)
= \(\frac{5}{9}-\frac{7}{13}-\frac{5}{3}.\frac{1}{13}+\frac{-5}{3}.\frac{2}{9}\)
=\(\frac{5}{9}-\frac{7}{13}-\frac{5}{39}+\frac{-10}{27}\)
=\(\frac{5}{9}+\frac{-7}{13}+\frac{-5}{39}+\frac{-10}{27}\)
=\(\frac{-13}{27}\)
Chúc bạn học tốt nhea ♥♥♥
25 tháng 4 2018
\(\frac{5}{9}-\frac{7}{13}-\frac{5}{9}.\frac{3}{13}+\frac{-5}{9}.\frac{61}{9}\)
\(=\frac{5}{9}\left(1-\frac{3}{13}\right)-\frac{7}{13}-\frac{5}{9}.\frac{61}{9}\)
\(=\frac{5}{9}.\frac{10}{13}-\frac{5}{9}.\frac{61}{9}-\frac{7}{13}\)
\(=\frac{5}{9}\left(\frac{10}{13}-\frac{61}{9}\right)-\frac{7}{13}\)\(=-\frac{314}{81}\)