which of the following ...

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factor26: Senior | Next Rank: 100 Posts; Posts: 99; Joined: Sun Mar 13, 2011 12:42 pm

by factor26 » Mon Feb 13, 2012 5:53 pm

which of the following must be equal to zero for all real numbers x?

I. -1/X

II. X+(-X)

III. X ^0

a - I only

b - II only

c - I and III only

d - II and III only

e - I, II, and III

OG answer is b - can someone please explain what they mean by all real numbers X?

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Source: Beat The GMAT — Problem Solving | Mon Feb 13, 2012 5:53 pm

pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

by pemdas » Mon Feb 13, 2012 6:22 pm

this implies all numbers you have studied so far, unless you were math major in college. From the content of your question I read you aren't math major and unaware of complex number operations, therefore consider this as all numbers you know - fractions, decimals, different sign numbers, absolutely all numbers (except for complex numbers).

Success doesn't come overnight!

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rijul007: Legendary Member; Posts: 588; Joined: Sun Oct 16, 2011 9:42 amFollowed by: 9 members; Location: New Delhi, India; Thanked: 130 times; GMAT Score:720

by rijul007 » Tue Feb 14, 2012 9:37 am

factor26 wrote:which of the following must be equal to zero for all real numbers x?

I. -1/X

II. X+(-X)

III. X ^0

a - I only

b - II only

c - I and III only

d - II and III only

e - I, II, and III

OG answer is b - can someone please explain what they mean by all real numbers X?

By all real number, they mean all the numbers that can be represented on the number line.

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