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! ♥
Tìm x biết : (1/1.2.3+1/2.3.4+................+1/8.9.10).x=23/45
\(\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}\text{ +}...\text{ +}\dfrac{1}{10.11.12}\)
chứng tỏ rằng
\(\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}+\dfrac{1}{3.4.5}+...+\dfrac{1}{98.99.100}>\dfrac{1}{4}\)
tim x
\(\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+......+\frac{1}{8.9.10}\right).x=\frac{23}{45}\)
tính
1/2+1/22+1/23+...............+1/210
1/1.2.3+1/2.3.4+.........+1/98.99.100
Tìm x biết: \(\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+....+\frac{1}{8.9.10}\right)\)x = \(\frac{23}{45}\)
Tính tổng: (\(\frac{1}{1.2.3}\) + \(\frac{1}{2.3.4}\) + \(\frac{1}{3.4.5}\) + ... + \(\frac{1}{98.99.100}\)).