\(B=70.\left(\frac{131313}{565656}+\frac{131313}{727272}+\frac{131313}{909090}\right)\)
\(B=70.\left(\frac{13}{56}+\frac{13}{72}+\frac{13}{90}\right)\)
\(B=70.13.\left(\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\right)\)
\(B=910.\left(\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)
\(B=910.\left(\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)
\(B=910.\left[\frac{1}{7}+\left(\frac{1}{8}-\frac{1}{8}\right)+\left(\frac{1}{9}-\frac{1}{9}\right)-\frac{1}{10}\right]\)
\(B=910.\left[\frac{1}{7}-\frac{1}{10}\right]\)
\(B=910.\frac{3}{70}=39\)
~ Hok tốt ~
#)Giải :
\(B=70.\left(\frac{131313}{565656}+\frac{131313}{727272}+\frac{131313}{909090}\right)\)
\(B=70.\left(\frac{13}{56}+\frac{13}{72}+\frac{13}{90}\right)\)( cùng chia cho 10101 )
\(B=70.\frac{39}{70}\)
\(B=39\)( trên dưới tử mẫu có 70 => loại )
#~Will~be~Pens~#
\(B=70.\left(\frac{131313}{565656}+\frac{131313}{727272}+\frac{131313}{909090}\right)\)
\(=70.\left(\frac{13}{56}+\frac{13}{72}+\frac{13}{90}\right)\)
\(=70.13.\left(\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)
\(=70.13.\left(\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)
\(=70.13.\left(\frac{1}{7}-\frac{1}{10}\right)=70.13.\frac{3}{70}\)
\(=\frac{7.13.3}{70}=39\)
\(B=70.\left(\frac{13}{56}+\frac{13}{72}+\frac{13}{90}\right)\)
\(\Leftrightarrow B=70.13.\left(\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)
\(\Leftrightarrow B=910.\left(\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)
\(\Leftrightarrow B=910.\left(\frac{1}{7}-\frac{1}{10}\right)=130-91=39.\)
