= 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

\(\frac{1}{3}-\frac{3}{5}+\frac{5}{7}-\frac{7}{9}+\frac{9}{11}-\frac{11}{13}+\frac{13}{15}+\frac{11}{13}-\frac{9}{11}+\frac{7}{9}-\frac{5}{7}+\frac{3}{5}-\frac{1}{3}\)

\(=\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{3}{5}-\frac{3}{5}\right)+\left(\frac{5}{7}-\frac{5}{7}\right)+\left(\frac{7}{9}-\frac{7}{9}\right)+\left(\frac{9}{11}-\frac{9}{11}\right)+\left(\frac{11}{13}-\frac{11}{13}\right)+\frac{13}{15}\)

\(=0+0+0+0+0+0+\frac{13}{15}\)

\(=\frac{13}{15}\)

= -59/105

k mình nha

k mình nha

\(P=\frac{6}{7}.\frac{8}{13}+\frac{6}{9}.\frac{9}{7}-\frac{3}{13}.\frac{6}{7}\)

\(P=\frac{6}{7}.\frac{8}{13}+\frac{6}{7}-\frac{3}{13}.\frac{6}{7}\)

\(P=\frac{6}{7}.\left(\frac{8}{13}+1-\frac{3}{13}\right)\)

\(P=\frac{6}{7}.\frac{18}{13}\)

\(P=\frac{108}{91}\)

\(\frac{6}{7}.\frac{8}{13}+\frac{6}{9}.\frac{9}{7}-\frac{3}{13}.\frac{6}{7}\)

= \(\frac{6}{7}.\left(\frac{8}{13}-\frac{3}{13}\right)+\frac{6}{9}.\frac{9}{7}\)

= \(\frac{6}{7}.\frac{5}{13}+\frac{54}{63}\)

= \(\frac{30}{91}+\frac{54}{63}\)

= \(\frac{30}{91}+\frac{6}{7}\)

= \(\frac{30}{91}+\frac{78}{91}\)

= \(\frac{108}{91}\)

Ta có : 

\(P=\frac{6}{7}.\frac{8}{13}+\frac{6}{9}.\frac{9}{7}-\frac{3}{13}.\frac{6}{7}\)

\(P=\frac{6}{7}.\frac{8}{13}+\frac{6}{7}-\frac{3}{13}.\frac{6}{7}\)

\(P=\frac{6}{7}.\frac{8}{13}+\frac{6}{7}.\frac{13}{13}-\frac{3}{13}.\frac{6}{7}\)

\(P=\frac{6}{7}.\left(\frac{8}{13}+\frac{13}{13}-\frac{3}{13}\right)\)

\(P=\frac{6}{7}.\frac{18}{13}\)

\(P=\frac{108}{91}\)

Tk mk nha !!! 

BẠN XEM LẠI CÁI ĐỀ XEM ĐÚNG KO

\(\frac{11}{12}.\frac{3.\left(1+\frac{1}{7}-\frac{1}{11}+\frac{1}{1001}-\frac{1}{13}\right)}{9.\left(\frac{1}{1001}-\frac{1}{13}+\frac{1}{7}-\frac{1}{11}+1\right)}=\frac{11}{12}.\frac{1}{3}=\frac{11}{36}\)

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

bằng 5/9 , chúc bạn học tốt !

B = \(\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)

Ta thấy có phân số \(\frac{5}{9}\) là thừa số chung

\(\Leftrightarrow\frac{5}{9}\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)=\frac{5}{9}\left(\frac{7+9+3}{13}\right)\)

\(=\frac{5}{9}.\frac{19}{13}\left(\frac{5.19}{9.13}\right)\)

\(=\frac{95}{117}\)

\(=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(\frac{3}{7}-\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(\frac{2}{11}-\frac{2}{11}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)+\frac{9}{16}\)

= 0 + \(\frac{9}{16}\)

= \(\frac{9}{16}\)

tick nha bn

\(B=\frac{1}{5}-\frac{3}{7}+\frac{5}{9}-\frac{2}{11}+\frac{7}{13}-\frac{9}{16}-\frac{7}{13}+\frac{2}{11}-\frac{5}{9}+\frac{3}{7}-\frac{1}{5}\)

    \(=\left(\frac{1}{5}-\frac{1}{5}\right)+\left(-\frac{3}{7}+\frac{3}{7}\right)+\left(\frac{5}{9}-\frac{5}{9}\right)+\left(-\frac{2}{11}+\frac{2}{11}\right)+\left(\frac{7}{13}-\frac{7}{13}\right)-\frac{9}{16}\)

    \(=0+0+0+0+0-\frac{9}{16}\)

    \(=-\frac{9}{16}\)

 ^...^  ^_^

cái này đăng hôm qua đến giờ 5 lần rồi,4 câu kia tui làm rồi vô chtt kiém coi có hk

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

bằng -9/16

B = 1 /5*(-3) /7 + 5 /9*(-2) /11 + 7 /13*(-9) /16*(-7) /13 + 2 /11*(-5) /9 + 3 /7*(-1) /5

B=-9/16

http://coccoc.com/search#query=T%C3%ADnh+nhanh+++B%3D+1%2F+5+%E2%88%92+3%2F+7+%2B+5%2F+9+%E2%88%92+2+%2F11+%2B+7%2F+13+%E2%88%92+9%2F+16+%E2%88%92+7+%2F13+%2B+2%2F+11+%E2%88%92+5%2F+9+%2B+3+%2F7+%E2%88%92+1%2F+5+

Ok

\(\frac{5}{9}-\frac{7}{13}-\frac{5}{9}.\frac{3}{13}+\frac{-5}{9}.\frac{6}{9}\)

= \(\frac{5}{9}-\frac{7}{13}-\frac{5}{3}.\frac{1}{13}+\frac{-5}{3}.\frac{2}{9}\)

=\(\frac{5}{9}-\frac{7}{13}-\frac{5}{39}+\frac{-10}{27}\)

=\(\frac{5}{9}+\frac{-7}{13}+\frac{-5}{39}+\frac{-10}{27}\)

=\(\frac{-13}{27}\)

Chúc bạn học tốt nhea ♥♥♥

\(\frac{5}{9}-\frac{7}{13}-\frac{5}{9}.\frac{3}{13}+\frac{-5}{9}.\frac{61}{9}\)

\(=\frac{5}{9}\left(1-\frac{3}{13}\right)-\frac{7}{13}-\frac{5}{9}.\frac{61}{9}\)

\(=\frac{5}{9}.\frac{10}{13}-\frac{5}{9}.\frac{61}{9}-\frac{7}{13}\)

\(=\frac{5}{9}\left(\frac{10}{13}-\frac{61}{9}\right)-\frac{7}{13}\)\(=-\frac{314}{81}\)

Ori Tinh Nghịch viết nhầm đề bài rồi nha ^^