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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
x=-3 doesn't work for B, right?
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
I think that the answer should be C, not B. Can you please correct me if I am wrong?
I did it in the following way:
I multiplied (|x| - 2)(x + 5)
x|x| + 5|x| -2x - 10 < 0

x|x| + 5|x| < 2x + 10

|x|(x + 5) < 2(x + 5)

I see that |x| should be smaller than 2.
|x| < 2
-2 < x < 2

One thing that I am not very confident about, can I multiply by |x|?
For example |x|(a + b), can I write it as (a|x| + b|x|)?

GreenlightTestPrep wrote:
Carcass wrote:
If (|x| - 2)(x + 5) < 0, then which of the following must be true?

A. x > 2
B. x < 2
C. -2 < x < 2
D. -5 < x < 2
E. x < -5


STRATEGY: Upon reading any GRE Multiple Choice question, we should always ask, Can I use the answer choices to my advantage?
In this case, we can easily test x-values that satisfy the given inequality.
Now let's give ourselves up to 20 seconds to identify a faster approach.
In this case, we can also attempt to solve the inequality, but the absolute value part of the inequality looks tricky. So, I'm pretty sure testing values is going to be a lot faster and much easier


Let's find an x-value that satisfies the inequality (|x| - 2)(x + 5) < 0.
x = 0 is an obvious solution, which means x = 0 must also be a solution to the correct answer choice.

Now plug x = 0 into each answer choice to get:
(A) 0 > 2. Not true. Eliminate.
(B) 0 < 2. True. KEEP.
(C) -2 < 0 < 2. True. KEEP.
(D) -5 < 0 < 2. True. KEEP.
(E) 0 < -5. Not true. Eliminate.

Now let's find another x-value that satisfies the inequality (|x| - 2)(x + 5) < 0.
I can see that x = -10 is a solution, since we get (|-10| - 2)((-10) + 5) < 0, which simplifies to be (8)(-5) < 0, which is true.

Now plug x = -10 into the three remaining answer choices:
(B) -10 < 2. True. KEEP.
(C) -2 < -10 < 2. Not true. Eliminate.
(D) -5 < -10 < 2. Not true. Eliminate.

By the process of elimination, the correct answer is B.
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If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
I think the anwer shd be 'e'

cause taking +x and -x conditions to break the modulus,

you would get equation: -5 < x < 2 (+x)
and

equation: x>-2 & x<-5 (-x)

since the question mentions "must" x shd be x<-5 cause all values in this range satify the condition

example, x=-6
(|-6|-2)(-6+5)=(4)(-1)<0 whereas in -2<x<2 we can take x=0 which does not satisfy the equation.
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
1
Expert Reply
If \((|x| - 2)(x + 5) < 0\), then which of the following must be true?

A. \(x > 2\)
B. \(x < 2\)
C. \(-2 < x < 2\)
D. \(-5 < x < 2\)
E. \(x < -5\)


\((|x| - 2)(x + 5) < 0\) means that \(|x| - 2\) and \(x + 5\) must have the opposite signs.

CASE 1: \(|x| - 2 > 0\) and \(x + 5 < 0\):

\(|x| - 2 > 0\) means that \(x < -2\) or \(x > 2\);

\(x + 5 < 0\) means that \(x < -5\).

Intersection of these ranges is \(x< -5\).

CASE 2: \(|x| - 2 < 0\) and \(x + 5 > 0\):

\(|x| - 2 < 0\) means that \(-2 < x < 2\);

\(x + 5 > 0\) means that \(x > -5\).

Intersection of these ranges is \(-2 < x < 2\).

So, we have that \((|x| - 2)(x + 5) < 0\) means that \(x < -5\) or \(-2 < x < 2\). ANY \(x\) from these possible ranges will for sure be less than 2 (option B).

To explaining other options:

\(x > 2\) (A) is not true because \(x\) could say be 0.

\(-2 < x < 2\) (C) is not true because \(x\) could say be -10.

\(-5 < x < 2\) (D) is not true because \(x\) could say be -10.

\(x < -5\) (E) is not true because \(x\) could say be 0.


Answer: B
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
Carcass wrote:
If \((|x| - 2)(x + 5) < 0\), then which of the following must be true?

A. \(x > 2\)
B. \(x < 2\)
C. \(-2 < x < 2\)
D. \(-5 < x < 2\)
E. \(x < -5\)


\((|x| - 2)(x + 5) < 0\) means that \(|x| - 2\) and \(x + 5\) must have the opposite signs.

CASE 1: \(|x| - 2 > 0\) and \(x + 5 < 0\):

\(|x| - 2 > 0\) means that \(x < -2\) or \(x > 2\);

\(x + 5 < 0\) means that \(x < -5\).

Intersection of these ranges is \(x< -5\).

CASE 2: \(|x| - 2 < 0\) and \(x + 5 > 0\):

\(|x| - 2 < 0\) means that \(-2 < x < 2\);

\(x + 5 > 0\) means that \(x > -5\).

Intersection of these ranges is \(-2 < x < 2\).

So, we have that \((|x| - 2)(x + 5) < 0\) means that \(x < -5\) or \(-2 < x < 2\). ANY \(x\) from these possible ranges will for sure be less than 2 (option B).

To explaining other options:

\(x > 2\) (A) is not true because \(x\) could say be 0.

\(-2 < x < 2\) (C) is not true because \(x\) could say be -10.

\(-5 < x < 2\) (D) is not true because \(x\) could say be -10.

\(x < -5\) (E) is not true because \(x\) could say be 0.


Answer: B



how can you take 0 when x<-5 shouldn't the possible range be [-inf, -5)
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
Expert Reply
Can you highlight specifically the part you are referring to sir ?
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
if x>2 how can it be x can take the value of 0

similarly, if x<-5 how can it take value of 0
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
Expert Reply
we are dealing with RANGE of x

Moreover, we must assess if the option MUST be true

We also tested various scenarios in which , in the end, the only reasonable value is that x <2

So for example A is NOT true because it says that x >2 NO

It is x < 2 and can be also 0, of course
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
I was stating option E not A as a potential answer since values where x<-5 would make the function negative thereby <0
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
1
SriSiddarth wrote:
Carcass wrote:
If \((|x| - 2)(x + 5) < 0\), then which of the following must be true?

A. \(x > 2\)
B. \(x < 2\)
C. \(-2 < x < 2\)
D. \(-5 < x < 2\)
E. \(x < -5\)


\((|x| - 2)(x + 5) < 0\) means that \(|x| - 2\) and \(x + 5\) must have the opposite signs.

CASE 1: \(|x| - 2 > 0\) and \(x + 5 < 0\):

\(|x| - 2 > 0\) means that \(x < -2\) or \(x > 2\);

\(x + 5 < 0\) means that \(x < -5\).

Intersection of these ranges is \(x< -5\).

CASE 2: \(|x| - 2 < 0\) and \(x + 5 > 0\):

\(|x| - 2 < 0\) means that \(-2 < x < 2\);

\(x + 5 > 0\) means that \(x > -5\).

Intersection of these ranges is \(-2 < x < 2\).

So, we have that \((|x| - 2)(x + 5) < 0\) means that \(x < -5\) or \(-2 < x < 2\). ANY \(x\) from these possible ranges will for sure be less than 2 (option B).

To explaining other options:

\(x > 2\) (A) is not true because \(x\) could say be 0.

\(-2 < x < 2\) (C) is not true because \(x\) could say be -10.

\(-5 < x < 2\) (D) is not true because \(x\) could say be -10.

\(x < -5\) (E) is not true because \(x\) could say be 0.


Answer: B



how can you take 0 when x<-5 shouldn't the possible range be [-inf, -5)


We are asked to determine which condition must be true. Another way to interpret this is to imagine which condition is satisfied for every x that is a solution to the equation. Since x = 0 is a solution, if E was the answer, 0 < -5 should be true (which it isn't). Thus, the answer is B because all the possible solutions satisfy it.
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Re: If (|x| - 2)(x + 5) < 0, then which of the following must be true? A. [#permalink]
Aquoravs wrote:
SriSiddarth wrote:
Carcass wrote:
If \((|x| - 2)(x + 5) < 0\), then which of the following must be true?

A. \(x > 2\)
B. \(x < 2\)
C. \(-2 < x < 2\)
D. \(-5 < x < 2\)
E. \(x < -5\)


\((|x| - 2)(x + 5) < 0\) means that \(|x| - 2\) and \(x + 5\) must have the opposite signs.

CASE 1: \(|x| - 2 > 0\) and \(x + 5 < 0\):

\(|x| - 2 > 0\) means that \(x < -2\) or \(x > 2\);

\(x + 5 < 0\) means that \(x < -5\).

Intersection of these ranges is \(x< -5\).

CASE 2: \(|x| - 2 < 0\) and \(x + 5 > 0\):

\(|x| - 2 < 0\) means that \(-2 < x < 2\);

\(x + 5 > 0\) means that \(x > -5\).

Intersection of these ranges is \(-2 < x < 2\).

So, we have that \((|x| - 2)(x + 5) < 0\) means that \(x < -5\) or \(-2 < x < 2\). ANY \(x\) from these possible ranges will for sure be less than 2 (option B).

To explaining other options:

\(x > 2\) (A) is not true because \(x\) could say be 0.

\(-2 < x < 2\) (C) is not true because \(x\) could say be -10.

\(-5 < x < 2\) (D) is not true because \(x\) could say be -10.

\(x < -5\) (E) is not true because \(x\) could say be 0.


Answer: B



how can you take 0 when x<-5 shouldn't the possible range be [-inf, -5)


We are asked to determine which condition must be true. Another way to interpret this is to imagine which condition is satisfied for every x that is a solution to the equation. Since x = 0 is a solution, if E was the answer, 0 < -5 should be true (which it isn't). Thus, the answer is B because all the possible solutions satisfy it.




Is 0 < -5. I think 0 > -5
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