= 1/2.(1/1.2 - 1/2.3 + 1/2.3 - 1/3.4 + 1/3.4 - 1/4.5 + 1/4.5 - ........+1/98.99 - 1/99.100 )
=1/2.(1/1.2 - 1/99.100)
=1/2 . 4949/9900
=4949/19800
chưng tỏ 1/1.2.3 +1/2.3.4 + 1/3.4.5+...+1/98.99.100=4949/19800
CMR: 1/(1.2.3)+1/(2.3.4)+...+1/(98.99.100)=4949/19800
chứng tỏ : \(\frac{1}{1.2.3}\)+\(\frac{1}{2.3.4}\)+\(\frac{1}{3.4.5}\)+.........+\(\frac{1}{98.99.100}\)= \(\frac{4949}{19800}\)
giải gấp mk nha! nếu đúng mh tick cho.
Tính nhanh
A=6+16+30+48+...+19600+19998
B=2+5+9+14+...+4949+5049
C=1.2.3+2.3.4+3.4.5+...+98.99.100
tính:A=\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{98.99.100}\)
A= 1.2.3 + 2.3.4 + 3.4.5 + ... + 98.99.100
Tính:\(A=1.2.3+2.3.4+3.4.5+...+98.99.100\)
\(\left[\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+..........+\frac{1}{98.99.100}\right].x=\frac{49}{200}\)
Tính giá trị biểu thức \(A=\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{97.98.99}+\frac{1}{98.99.100}\) .Khi đó : \(A=?\)