\(2S=1+\frac{1}{2^2}+\frac{1}{2^3}+...........+\frac{1}{2^8}\)
\(2S-S=1+\frac{1}{2^2}-\frac{1}{2}-\frac{1}{2^9}\)
\(S=1+\frac{1}{4}-\frac{2}{4}-\frac{1}{2^9}\)
\(S=1-\frac{1}{4}-\frac{1}{2^9}\)
\(S=\frac{3}{4}-\frac{1}{2^9}\)
\(S=\frac{3.128-1}{2^9}=\frac{383}{512}\)
TÍNH NHANH
1) S= 1/1*2+1/2*3+1/3*4+...+1/99*100
2) S= 3/1*3+3/3*5+2/5*7+...+2/97*99
3) S= 4/5*7+4/7*9+4/9*11+...+4/59*61
Tính các tổng sau:
1, S=1-2+3_4+..+25-26
2, S=1-3+5-7+...+49-51
3, S=-1+3-5+7-...-53+55
4, S=2-4+6-8+...+22-24
5, S=-2+4-6+8-...-26+28
6, S=2-5+8-11+...-29+32
7, S=-1+5-9-13-...-41-45
8, S=1-5+9-13+...++89-93
9, S=2-4+6-8+...+202-204
10, S=1-6=11-16+21-26+...+171-176
huhu giúp mình với ạ 2h chiều nay mình phải nộp r =(((
S=1/2^2+1/3^2+1/4^2+1/5^2+1/6^2+...+1/9^2, chứng minh 2/5<S<8/9
S=1/2^2 + 1/3^2 + 1/4^2 +...+ 1/9^2. Chứng minh rằng 2/5 < S <8/9
Chưng tỏ
a, S= 1/2^2+1/3^2+...+1/9^2
Chứng tỏ 2/5<S<8/9
b, 1/2-1/4+1/8-1/16+1/32-1/64<1/3
c, 1/3-2/3^2+3/3^3-4/3^4+...+99/3^99-100/3^100<3/16
S=1/2^2 + 1/3^2 + 1/4^2 +...+ 1/9^2
Chứng minh: 2/5<S<8/9
cho s =1/22+1/3^2+1/4^2+...........+1/9^2. cmr:2/5 < s < 8/9
cho S= 1/2^2+1/3^2+1/4^2+.....+1/9^2
c/m 2/5<s<8/9
Cho tong S = 1/2^2 + 1/3^2 +1/4^2 +.....+ 1/9^2
CMR : 2/5 < S <8/9
tính tổng s=(1/2+1/3+1/4+...+1/10)+(2/3+2/4+...+2/10)+...+(8/9+8/10)+9/10
