Tính B=1+1/2(1+2)+1/3(1+2+3)+1/4(1+2+3+4)+...+1/20(1+2+3+4+...+20)
Tính B = \(1+\frac{1}{2}.\left(1+2\right)+\frac{1}{3}.\left(1+2+3\right)+\frac{1}{4}.\left(1+2+3+4\right)+....+\frac{1}{20}.\left(1+2+3+...+20\right)\)
Phong cần gấp
Mong đc giúp đỡ
Tính \(B=1+\dfrac{1}{2}\left(1+2\right)+\dfrac{1}{3}\left(1+2+3\right)+\dfrac{1}{4}\left(1+2+3+4\right)+...+\dfrac{1}{20}\left(1+2+3+...+20\right)\)
1)Tính nhanh: A=1+3+3^2+3^3+3^4+...+3^100
B= 1+4^2+4^4+4^6+...+4^100
2) Cho biết 1^2+2^3+3^2+4^2+...+10^2= 385
Tính a) S1= 2^2+4^2+...+20^2
. b) S2= 100^2+200^2+...1000^2
Tính
1+\(\frac{1}{2}\).(1+2)+\(\frac{1}{3}\). (1+2+3)+\(\frac{1}{4}\).(1+2+3+4)+...+\(\frac{1}{20}\).(1+2+3+...+20)
Các pn giúp mk giải bài na
3/2 + 1/2 + 1/4 + 3/20 + 1/10 + 1/14 + 3/56 + 1/24
1) Tính
A = 1 + \(\dfrac{1}{2}\) . (1+2) + \(\dfrac{1}{3}\) . (1+2+3) + \(\dfrac{1}{4}\) . (1+2+3+4) +...+ \(\dfrac{1}{20}\) . (1+2+...+20)
mong các bạn làm giúp mình
a, D = \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}\)
b, E = \(\dfrac{1}{1+2}+\dfrac{1}{1+2+3}+\dfrac{1}{1+2+3+4}+.......+\dfrac{1}{1+2+3+.......+9}\)
tính:
B=\(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+........+\frac{1}{2^{10}}\)
C=\(\frac{4^{20}+4^{29}}{8^{13}+8^{15}}\)
