I need help

This topic has expert replies
Junior | Next Rank: 30 Posts
Posts: 18
Joined: 18 May 2007

I need help

by rajt » Fri May 18, 2007 4:05 pm
Can you help me solve this?
Attachments
q6.GIF

User avatar
Community Manager
Posts: 789
Joined: 28 Jan 2007
Location: Silicon valley, California
Thanked: 30 times
Followed by:1 members

Re: I need help

by jayhawk2001 » Fri May 18, 2007 4:36 pm
rajt wrote:Can you help me solve this?
You have to see the pattern here

(-1)^2*1/2 + (-1)^3*1/2^2 + ... + (-1)^11* 1/2^10

Take all positive and negative values separately

1/2 (1 + 1/2^2 + ... + 1/2^8 ) - 1/2^2 * (1 + 1/2^2 + ... + 1/2^8 )

= (1/2 - 1/4) * (1 + 1/2^2 + ... + 1/2^8 )
= 1/4 * (1 + 1/2^2 + ... + 1/2^8 )

This is greater than 1/4 but less than 1/2

Is it D ?

Junior | Next Rank: 30 Posts
Posts: 18
Joined: 18 May 2007

by rajt » Fri May 18, 2007 7:22 pm
yes the answer is D. Your explanation is pretty clear.