Tính tổng sau : A = 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + ... + 99 - 100
B=1–2- 3+4+5-6-7+8+...+97-98-99+100
Tính tổng sau:
a) 1 - 2 + 3 - 4 + ... + 99 - 100
b) 2 - 4 + 6 - 8 + ... + 48 - 50
c) 1 + 2 - 3 + 4 - ... - 99 + 100
TÍNH NHANH
a) A= 1 . 2 + 2 . 3 + 3 .4 +...+ 98 . 97
b) B= 1 + 1/2 + 1/4 + 1/8 +...+ 1/1024
lam vay co duoc ko
1/2+1/4+1/8+... +1/512+1/1024=1-1/2+1/2-1/4+...+1/512-1/1024=1-1/1024=1/1023
CM Bất đẳng thức:
a,A=1/2+1/4+1/8+...+1/1024 < 1/2
b,B= 1/+1/4+1/16+1/64+...+1/256 < 3/2
Tính tổng
A) A= 1+2+3+...+100
B) B= 2+4+6+...+120
C) A= 3+5+8+...+99
D) B= 3+6+9+...123
1. (1+1/2).(1+1/2^2).(1+1/2^3)....(1+1/2^100) < 3
2. 1/(5+1)+2/(5^2+1)+4/(5^4+1)+...+ 1024/(5^1024+1) <1/4
3. 3/(1!+2!+3!)+4/(2!+3!+4!)+...+100/(98!+99!+100!) <1/2
chứng minh rằng
a , \(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{8}-\dfrac{1}{16}+...+\dfrac{1}{512}-\dfrac{1}{1024}\) < \(\dfrac{1}{3}\)
b , \(\dfrac{1}{3}-\dfrac{2}{3^2}+\dfrac{3}{3^3}-\dfrac{4}{3^4}+...+\dfrac{99}{3^{99}}-\dfrac{100}{3^{100}}\) < \(\dfrac{3}{16}\)
a=1/2-1/4+1/8-...-1/1024