Các câu hỏi tương tự
tính B = (80 - 1/9 - 2/10-3/11- 4/12-...-80/88):(1/45+1/50+1/55+...+1/440)
C=1+3+3^2+3^3+....+3^80
a) 25. (36+80) + 36. (75+80)
b) S2= 1 . 2 + 2 . 3 + 3 . 4 + 4 . 5 + ... + 99 . 100
\(S3= 1^2 + 2^2 + 3^2 + ... + 99^2\)
1/ 76 - (2x - 1)\(^2\) = 51
2/ 3x × 3 - 1 = 80
1/1x1/2+1/2x1/3+1/3x1/4+...+1/79x1/80
chứng minh :1+1/2+1/3+1/4+...+1/80 <6
So sánh:
a) (1/80) mũ 7 & (1/243) mũ 6
b) (3/8) mũ 5 & (5/243) mũ 3
(80% . x - x/3):(-4)=1/2
A=1-2+3-4+...+79-80