A = 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56
A = (1/6 + 1/12) + 1/20 + 1/30 + 1/42 + 1/56
A = 1/4 + 1/20 + 1/30 + 1/42 + 1/56
A = (1/4 + 1/20) + 1/30 + 1/42 + 1/56
A = 3/10 + 1/30 + 1/42 + 1/56
A = (3/10 + 1/30) + 1/42 + 1/56
A = 1/3 + 1/42 + 1/56
A = (1/3 + 1/42) + 1/56
A = 5/14 + 1/56
A = 3/8
a) Tính :
\(1-\dfrac{1}{2};\dfrac{1}{2}-\dfrac{1}{3};\dfrac{1}{3}-\dfrac{1}{4};\dfrac{1}{4}-\dfrac{1}{5};\dfrac{1}{5}-\dfrac{1}{6}\)
b) Sử dụng kết quả của câu a) để tính nhanh tổng sau :
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}\)
giúp mình nha mình đang cần ngay bây giờ , bạn nào làm nhanh nhất mình sẽ tick cho nha !
\(\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}+\dfrac{1}{110}+\dfrac{1}{132}+\dfrac{1}{156}+\dfrac{1}{182}+\dfrac{1}{210}=\)
Tính
B=\(\dfrac{3}{2}-\dfrac{5}{6}+\dfrac{7}{12}-\dfrac{9}{20}+\dfrac{11}{30}-\dfrac{13}{42}+\dfrac{15}{56}\)
Tính :
a) \(\dfrac{3}{5}-\dfrac{-7}{10}-\dfrac{13}{-20}\)
b) \(\dfrac{3}{4}+\dfrac{-1}{3}-\dfrac{5}{18}\)
c) \(\dfrac{3}{14}-\dfrac{5}{-8}+\dfrac{-1}{2}\)
d) \(\dfrac{1}{2}+\dfrac{1}{-3}+\dfrac{1}{4}-\dfrac{-1}{6}\)
Tính nhanh :
\(C=\dfrac{1}{2}+\dfrac{1}{14}+\dfrac{1}{35}+\dfrac{1}{65}+\dfrac{1}{104}+\dfrac{1}{152}\)
Điền phân số thích hợp vào ô trống :
a) \(\dfrac{1}{12}+.....=\dfrac{-2}{3}\)
b) \(\dfrac{-1}{3}+......=\dfrac{2}{5}\)
c) \(\dfrac{1}{4}-......=\dfrac{1}{20}\)
d) \(\dfrac{-8}{13}-......=0\)
Tính nhanh :
\(B=\dfrac{1}{15}+\dfrac{1}{35}+\dfrac{1}{63}+\dfrac{1}{99}+\dfrac{1}{143}\)
Tính nhanh: \(C=\dfrac{1}{2}+\dfrac{1}{14}+\dfrac{1}{35}+\dfrac{1}{65}+\dfrac{1}{104}+\dfrac{1}{152}\)
giúp mik nhé
Tìm \(x\) biết :
a) \(x-\dfrac{3}{4}=\dfrac{1}{2}\)
b) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)
