1/1x2 + 1/2x3 + 1/3x4 + ... + 1/24x25
= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/24 - 1/125
= 1 - 1/25
= 24/25
1/1x2 + 1/2x3 + 1/ 3x4 +.....+ 1/24x25
= ( 1- 1/2) + (1/2-1/3) + (1/3 - 1/4)+........+ (1/24-1/25)
= 1-1/2+1/2-1/3+1/3-1/4+.........+1/24-1/25
= 1- 1/25 = 24/25
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{24.25}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{24}-\frac{1}{25}\)
\(=1-\frac{1}{25}=\frac{24}{25}\)
Ủng hộ mk nha ^_^
