\(=\left(\dfrac{7}{18}+\dfrac{3}{34}\right):\left[\dfrac{14}{4}\left(\dfrac{1}{9}-\dfrac{1}{13}+\dfrac{1}{14}-\dfrac{1}{18}+\dfrac{1}{13}-\dfrac{1}{17}\right)\right]\)

\(=\dfrac{73}{153}:\left[\dfrac{14}{4}\cdot\dfrac{73}{1071}\right]\)

\(=\dfrac{73}{153}:\dfrac{73}{306}=2\)

\(P=\left(\frac{7.9}{9.18}+\frac{7.3}{2.7.17}\right):\left(\frac{14}{117}+\frac{1}{18}+\frac{14}{221}\right)\)

\(P=\left(\frac{7}{18}+\frac{3}{34}\right):\left(..\right)\)

Tới đây bạn tự làm nốt.

bạn có thể gúp mình chi tiết hơn được không 

mình làm được rồi

a) Ta có: \(A=\left(\dfrac{63}{9\cdot18}+\dfrac{21}{14\cdot17}\right):\left(\dfrac{14}{9\cdot13}+\dfrac{14}{14\cdot18}+\dfrac{14}{3\cdot17}\right)\)

\(=\left(7\cdot\dfrac{9}{9\cdot18}+7\cdot\dfrac{3}{14\cdot17}\right):\left(14\left(\dfrac{1}{9\cdot13}+\dfrac{1}{14\cdot18}+\dfrac{1}{3\cdot17}\right)\right)\)

\(=\dfrac{7\left(\dfrac{1}{9}-\dfrac{1}{18}+\dfrac{1}{14}-\dfrac{1}{17}\right)}{14\cdot\dfrac{1}{4}\cdot\left(\dfrac{4}{9\cdot13}+\dfrac{4}{3\cdot17}+\dfrac{4}{14\cdot18}\right)}\)

\(=\dfrac{\dfrac{1}{9}-\dfrac{1}{18}+\dfrac{1}{14}-\dfrac{1}{17}}{\dfrac{1}{2}\left(\dfrac{1}{9}-\dfrac{1}{13}+\dfrac{1}{3}-\dfrac{1}{17}+\dfrac{1}{14}-\dfrac{1}{18}\right)}\)

\(=\dfrac{\dfrac{73}{1071}}{\dfrac{1}{2}\cdot\dfrac{4519}{13923}}=\dfrac{1898}{4519}\)

\(A=\dfrac{14}{8.11}+\dfrac{14}{11.14}+\dfrac{14}{14.17}+.....+\dfrac{14}{197.200}\)

\(A=\dfrac{14}{3}\left(\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}+\dfrac{1}{14}-\dfrac{1}{17}+...+\dfrac{1}{197}-\dfrac{1}{200}\right)\)

\(A=\dfrac{14}{3}.\left(\dfrac{1}{8}-\dfrac{1}{200}\right)\)

\(A=\dfrac{14}{3}.\dfrac{24}{200}=\dfrac{28}{25}\)

\(B=\dfrac{7}{15}+\dfrac{7}{35}+\dfrac{7}{63}+...+\dfrac{7}{399}\)

\(B=\dfrac{7}{3.5}+\dfrac{7}{5.7}+\dfrac{7}{7.9}+.....\dfrac{7}{19.21}\)

\(B=\dfrac{7}{2}\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+....+\dfrac{1}{19}-\dfrac{1}{21}\right)\)

\(B=\dfrac{7}{2}.\left(\dfrac{1}{3}-\dfrac{1}{21}\right)\)

\(B=\dfrac{7}{2}.\dfrac{6}{21}=1\)

1.-14*63+(-14)*37=-14*(63+37)=-14*100=-1400

2.-21*21+21*(-79)=21*[-21+(-79)]=21*(-100)=-2100

cho mình nha!Thank you!

1. = - 14* ( 63 + 37) 

    = -14*100

    = -1400

2. = [ -21 + ( -79) ] *21

   = ( - 100) * 21

   = - 2100

1. = - 14.( 63 + 37 ) = - 14 . 100 = - 1400

2. = 21.[ ( - 21 ) + ( - 79 ) ] = 21.( - 100 ) = - 2100

=1/9 chắc vậy :v