chứng tỏ rằng
\(\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}+\dfrac{1}{3.4.5}+...+\dfrac{1}{98.99.100}>\dfrac{1}{4}\)
Cho :
\(A=\dfrac{5}{1.2.3}+\dfrac{8}{2.3.4}+\dfrac{11}{3.4.5}+...+\dfrac{6056}{2018.2019.2020}\)
Hãy so sánh A với 2
Bài 2: Tính tổng: ( Dấu . là nhân nhé)
A=\(\dfrac{1}{1.2.3}\)+\(\dfrac{1}{2.3.4}\)+\(\dfrac{1}{3.4.5}\)+.......+\(\dfrac{1}{37.38.39}\)
B=\(\dfrac{5}{1.2.3}\)+\(\dfrac{5}{2.3.4}\)+......+\(\dfrac{5}{18.19.20}\)
C=\(\dfrac{6}{1.2.3}\)+\(\dfrac{6}{2.3.4}\)+\(\dfrac{6}{3.4.5}\)+......+\(\dfrac{6}{18.18.20}\)
D=100+ 98 +96+ ....+ 2-1-3-......+95- 97- 99.
Ai biết làm ý nào thì giúp mik ghi cách làm ra nhé!
mik đang cần gấp
Cảm ơn nhiều! ♥
1. Tính
a. S = \(\dfrac{1}{1.4}\)+\(\dfrac{1}{4.7}\)+\(\dfrac{1}{7.10}\)+.......+\(\dfrac{1}{2002.2005}\)
b. P = \(\dfrac{3}{1.6}\)+\(\dfrac{3}{6.11}\)+\(\dfrac{3}{11.16}\)+.......+\(\dfrac{3}{96.101}\)
c. Q = \(\dfrac{1}{1.2.3}\)+\(\dfrac{1}{2.3.4}\)+\(\dfrac{1}{3.4.5}\)+.......+\(\dfrac{1}{98.99.100}\)
Help me!
\(\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}\text{ +}...\text{ +}\dfrac{1}{10.11.12}\)
Tính nhanh:
\(B=\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}\)
Bài 1: Tính nhanh: \(\dfrac{4}{3.7}+\dfrac{4}{7.11}+\dfrac{4}{11.15}+\dfrac{4}{15.19}+\dfrac{4}{19.23}+\dfrac{4}{23.27}\)
Tính nhanh
\(\dfrac{3}{2^2}.\dfrac{8}{3^2}.\dfrac{15}{4^2}...\dfrac{899}{30^2}\)
Tính:
a) \(45\dfrac{10}{63}-44\dfrac{25}{84}\)
b) \(\left(2\dfrac{1}{3}-1\dfrac{1}{9}\right):4-\dfrac{3}{4}\)
Nhanh nhé ai nhanh mik tick cho!