1\2+1\2^2+1\2^3+1\2^4+.....+1\2^n的值为几?
有过程.
\为分数线
參考答案:设A=1\2+1\2^2+1\2^3+1\2^4+.....+1\2^n
1/2A=1/2^2+1/2^3+1/2^4+...+1/2^(n+1)
A-1/2A=1/2-1/2^(n+1)
1/2A=1/2[1-1/2^n]
A=1-1/2^n
1\2+1\2^2+1\2^3+1\2^4+.....+1\2^n的值为几?
有过程.
\为分数线
參考答案:设A=1\2+1\2^2+1\2^3+1\2^4+.....+1\2^n
1/2A=1/2^2+1/2^3+1/2^4+...+1/2^(n+1)
A-1/2A=1/2-1/2^(n+1)
1/2A=1/2[1-1/2^n]
A=1-1/2^n