Các bn ơi giúp mk vs nha mấy bn!!
Câu 1: Tìm x, biết
a, x = \(\dfrac{1}{4}\) + \(\dfrac{2}{13}\)
b, \(\dfrac{x}{3}\) = \(\dfrac{2}{3}\) + \(\dfrac{-1}{7}\) +
Câu 3: Tính nhanh:
a, \(\dfrac{-2}{5}\) +\(\dfrac{3}{-4}\) + \(\dfrac{6}{7}\) + \(\dfrac{3}{4}\) + \(\dfrac{2}{5}\)
b, \(\dfrac{7}{15}\) + \(\dfrac{4}{-9}\) + \(\dfrac{-2}{11}\) + \(\dfrac{8}{15}\) + \(\dfrac{-5}{9}\)
c, \(\dfrac{-5}{7}\) + \(\dfrac{5}{13}\) +\(\dfrac{-20}{41}\) + \(\dfrac{8}{13}\) + \(\dfrac{-21}{41}\)
Câu 1:
a,\(x=\dfrac{1}{4}+\dfrac{2}{13}\)
\(x=\dfrac{13}{52}+\dfrac{8}{52}=\dfrac{21}{52}\)
Câu 2:
a,\(\dfrac{-2}{5}+\dfrac{3}{-4}+\dfrac{6}{7}+\dfrac{3}{4}+\dfrac{2}{5}\)
\(=\left(\dfrac{-2}{5}+\dfrac{2}{5}\right)+\left(\dfrac{3}{-4}+\dfrac{3}{4}\right)+\dfrac{6}{7}\)
=\(0+0+\dfrac{6}{7}=\dfrac{6}{7}\)
b,\(\dfrac{7}{15}+\dfrac{4}{-9}+\dfrac{-2}{11}+\dfrac{8}{15}+\dfrac{-5}{9}\)
=\(\left(\dfrac{7}{15}+\dfrac{8}{15}\right)+\left(\dfrac{4}{-9}+\dfrac{-5}{9}\right)+\dfrac{-2}{11}\)
=\(\dfrac{15}{15}+\dfrac{-9}{9}+\dfrac{-2}{11}=1+\left(-1\right)+\dfrac{-2}{11}\)
=\(0+\dfrac{-2}{11}=\dfrac{-2}{11}\)
c, \(\dfrac{-5}{7}+\dfrac{5}{13}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)
=\(\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)
=\(\dfrac{13}{13}+\dfrac{-41}{41}+\dfrac{-5}{7}=1+\left(-1\right)+\dfrac{-5}{7}\)
=\(0+\dfrac{-5}{7}=\dfrac{-5}{7}\)
aF CÂU B BÀI 1 Á. mK VIẾT THỪA ĐIA 1 DẤU "+'
