Dấu "." là dấu nhân bạn nhé.
Ta có:
\(A=1+\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+...+\dfrac{1}{729.3}\)
\(\Rightarrow3A=3+1+\dfrac{1}{3}+\dfrac{1}{9}+...+\dfrac{1}{729}\)
\(\Rightarrow3A-A=3-\dfrac{1}{729.3}\)
\(\Rightarrow2A=3-\dfrac{1}{729.3}\)
\(\Rightarrow A=\dfrac{1}{2}\left(3-\dfrac{1}{729.3}\right)\)
A=1+1/3+1/9+1/27+...+1/729x3
tính giá trị biểu thức: 1+ 1/3 + 1/9 + 1/27 + .....+ 1/729x3
a) 1+1/3 + 1/9 + 1/27 + 1/81
(a+1/1.3)+(a+1/3.5)+(a+1/5.7)+...+(a+1/23.25)=11.a+(1/3+1/9+1/27+1/81+1/243)
A=1+1/3+1/9+1/27+1/81+......+1/729 tính nhanh tổng
\(A=1+\dfrac{1}{3}+\dfrac{1}{9}+\dfrac{1}{27}+\dfrac{1}{81}+\dfrac{1}{243}+\dfrac{1}{729}\)
Tính A
tính nhanh : A = 1/3 + 1/9 + 1/27 + 1/81+.....+1/59049
Tính giá trị biểu thức: A= 1/3+1/9+1/27+1/81+1/243
a,1+1/2+1/4+1/8+1/16 b,2+2/3+2/9+2/27
