\(\frac{1}{1.6}+\frac{1}{6.11}+...+\frac{1}{96.101}\)
\(=\frac{1}{5}.\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+...+\frac{1}{96}-\frac{1}{101}\right)\)
\(=\frac{1}{5}.\left(1-\frac{1}{101}\right)\)
\(=1.\frac{100}{101}\)
\(=\frac{100}{101}\)
tính 1/1x6 + 1/6x11 +...+ 1/96x101
CMR:1/1x6+1/6x11+1/11x16+....+1/(5n+1)(5n+6)=n+1/5n+6
1/1x6+1/6x11+...+1/(5n+1)x(5n+6)=n+1/5n+6
chứng minh công thức
5/1x6+5/11x16+...+5/96x101
Chứng minh với n thuộc N có:
1 / 1x6 + 1/ 6x11 + ... + 1/ ( 5n + 1 ) x ( 5n + 6 ) = n + 1 / 5n + 6
chứng minh
1/1x6+1/6x11+...+1/(5n+1)(5n-6)=3/11
1/1x2x3+1/2x3x4+...1/18x19x20<1/4
x = 1x6+6x11+11x6+....+51x56
-(x/2) + 2x/3 + (x+1)/4 + (2x+1)/6 = 3/8
3/(2x+1) + 10/(4x+2) - 6/(6x+3)=12/26
5/1x6 + 5/ 6x11 + ... +5/(5x+1)(5x+6)=2005/2006
-(x/2) + 2x/3 + (x+1)/4 + (2x+1)/6 = 3/8
3/(2x+1) + 10/(4x+2) - 6/(6x+3)=12/26
5/1x6 + 5/ 6x11 + ... +5/(5x+1)(5x+6)=2005/2006
