Tìm: \(\frac{x-2}{3}+\frac{x-2}{3.5}+\frac{x-2}{5.7}+...+\frac{x-2}{97.99}=\frac{-49}{99}\)
Tính: 2/1.3+ 2/3.5+ 2/5.7+ ......... + 2/97.99
1.Tính hợp lí
a/ 2/3.5 + 2/5.7 + 2/7.9 +...+2/97.99
b/ 1/3.5 + 1/5.7 + 1/7.9 +...+1/97.99
c/1/18 + 1/54 + 1/108 +...+1/990
2.Chứng minh rằng: 1/14 + 1/42 + 1/43 +...+1/79 + 1/80 > 7.12
Tính tổng: a) S= 1^2+2^2+3^2+...+99^2
b) S= 1.3+3.5+5.7+...+97.99
tính:a/\(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+......+\frac{2}{97.99}\)
Tính GTBT:1.3/3.5+2.4/5.7+3.5/7.9+...+48.50/97.99
Tính: A=1.3+3.5+5.7+....+97.99
1/ A = 12- 22 + 32 - 42+...+ 992- 1002
2/ A = 1.3 + 3.5 + 5.7 +...+ 97.99 + 99.100
3/ A = 2.4 + 4.6 + 6.8 +...+ 99.100 + 100.102
tính D=2.4+3.5+4.6+5.7+6.8+7.9+.......+97.99+98.100