f****n
发帖数: 208 | 1 I am so rusty with the college math. Here is the question:
f(n) = 1*2^0 + 2*2^1 + 3*2^2 + ... + n * 2^(n-1)
What is f(n)? Please help. |
Q***5
发帖数: 994 | 2 Consider g(x) = x^1+x^2+ ... x^n, you can derive the explicit
formula of g(x) = (x^(n+1)-1)/(x-1)
Then your f(n) = g'(2), the derivative of g at 2.
【在 f****n 的大作中提到】
: I am so rusty with the college math. Here is the question:
: f(n) = 1*2^0 + 2*2^1 + 3*2^2 + ... + n * 2^(n-1)
: What is f(n)? Please help.
|
N***m
发帖数: 4460 | 3 20498，你们这么问作业不好
【在 f****n 的大作中提到】
: I am so rusty with the college math. Here is the question:
: f(n) = 1*2^0 + 2*2^1 + 3*2^2 + ... + n * 2^(n-1)
: What is f(n)? Please help.
|
f****n
发帖数: 208 | 4 Cool. Now I remember. It is actually college math 101. Thanks for reminding
me.
【在 Q***5 的大作中提到】
: Consider g(x) = x^1+x^2+ ... x^n, you can derive the explicit
: formula of g(x) = (x^(n+1)-1)/(x-1)
: Then your f(n) = g'(2), the derivative of g at 2.
|
