The U means UNION.
If you have 2 groups, then this is saying that x belongs to group that is shared by both, meaning where the groups are the same, also referred to as UNION, like in Venn Diagrams.
With b), You have the group of -1,0, and then 1,infinity.
It appears that B is saying that the only values that satisfy the question are 1, -1, 0, and infinity. It is a confusing question, but you can also arrive at the answer of B by process of elimination.
____ = X, Which of the following must be true for all X?
a) x>1 Incorrect. MUST BE TRUE, but is x = 2, then 2/|2| = 1, not 2 which is X.
b) x (BELONGS TO) (-1,0)U(1,infinity)
c) |x|<1 This means |x| is a positive or negative fraction. Not true 1/2 divided by 1/2 = +1, not x which is 1/2 here
d) |x|=1 The question asks for "all X" meaning we must consider all possible values for x. |x| = 1 is one part of the answer, but it ignores -1 and 0. (and I guess infinity?) Since the question asks for "all X" this isn't a complete answer.
e) |x|^2>1 This looks like a filler answer where the authors just needed something for answer e). If the square of |x| is greater than 1, then x the following must be true. x < -1 or x > 1. If we eliminated d because it was an incomplete answer, then there are multiple reasons to exclude this one. -1 and 1 satisfy the question stem, but it also appears to say that x > 1 would satisfy the question also, but this isn't true. x = 2 and we already know 2 is not a valid value of x.
i could not understand the meaning.. pls explain
OA is B.
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.
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