Câu 2: Trang 26 sách toán VNEN lớp 6 tập 2
Tính nhanh giá trị mỗi biểu thức sau:
$A = \frac{18}{26}\;+\;\frac{-5}{27}\;+\;\frac{-22}{86}\;+\;\frac{12}{39}\;+\;\frac{-32}{43}$
$B = \frac{-10}{12}\;+\;\frac{8}{15}\;+\;\frac{-19}{56}\;+\;\frac{3}{-18}\;+\;\frac{28}{60}$
Bài Làm:
$A = \frac{18}{26}\;+\;\frac{-5}{27}\;+\;\frac{-22}{86}\;+\;\frac{12}{39}\;+\;\frac{-32}{43}$
$A = \frac{9}{13}\;+\;\frac{-5}{27}\;+\;\frac{-11}{43}\;+\;\frac{4}{13}\;+\;\frac{-32}{43}$
$A = (\frac{9}{13}\;+\;\frac{4}{13})\;+\;(\frac{-11}{43}\;+\;\frac{-32}{43}\;+\;\frac{-5}{27}$
$A = 1\;+\;(-1)\;+\;\frac{-5}{27}$
$A = \frac{-5}{27}$.
$B = \frac{-10}{12}\;+\;\frac{8}{15}\;+\;\frac{-19}{56}\;+\;\frac{3}{-18}\;+\;\frac{28}{60}$
$B = \frac{-5}{6}\;+\;\frac{8}{15}\;+\;\frac{-19}{56}\;+\;\frac{-1}{6}\;+\;\frac{7}{15}$
$B = (\frac{-5}{6}\;+\;\frac{-1}{6})\;+\;(\frac{8}{15}\;+\;\frac{7}{15})\;+\;\frac{-19}{56}$
$B = (-1)\;+\;1\;+\;\frac{-19}{56}$
$B = \frac{-19}{56}$.