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If x is any integer from -6 to 2 inclusive, how many [#permalink]
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GMATPrepNow wrote:
If x is any integer from -6 to 2 inclusive, how many values of x satisfy the following inequality: 2 - |x³ + 10x² - 24x| < 2 ?

A) 5
B) 6
C) 7
D) 8
E) 9

*Kudos for all correct solutions


2 - |x³ + 10x² - 24x| < 2
=|x³ + 10x² - 24x| > 0 (cancelling 2 both sides and multiplying by -1 both sides ,flipping the sign)
factor out:- x³ + 10x² - 24x = x(x-2)(x+12)
After removing mod sign,Two cases:-
Case 1:-
if x(x-2)(x+12) > 0
then -12<x<0 & x>2
but as x is integer between -6 & 2 x satisfies for -6,-5,-4,-3,-2,-1 (5 nos.)

Case 2:-
if x(x-2)(x+12) < 0
then x<-12 & 0<x<2
but as x is integer between -6 & 2 x satisfies for 1 (1 nos.)

x cannot be 0 & 2 or -12(not in range) ..because then inequality does not hold and equation =0

Total satisfying values =-6,-5,-4,-3,-2,-1(case 1) && 1(case 2)=7nos.

Ans C

Originally posted by rohit8865 on 24 Oct 2016, 20:39.
Last edited by rohit8865 on 29 Nov 2016, 10:48, edited 1 time in total.
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If x is any integer from -6 to 2 inclusive, how many [#permalink]
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-6: 2 - |(-6)(-8)(6)| < 2 - VALID
-5: 2 - |(-5)(-7)(7)| < 2 - VALID
-4: 2 - |(-4)(-6)(8)| < 2 - VALID
-3: 2 - |(-3)(-5)(9)| < 2 - VALID
-2: 2 - |(-2)(-4)(10)| < 2 - VALID
-1: 2 - |(-1)(-2)(11)| < 2 - VALID
0: 2 - |0| < 2 - INVALID
1: 2 - |1(-1)(13)| < 2 - VALID
2: 2 - |0| < 2 - INVALID

Interior (of the abs value) can be rewritten as: 2 - |x(x-2)(x+12)| < 2 --> This is why 2 and 0 do not work for this eqn
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Re: If x is any integer from -6 to 2 inclusive, how many [#permalink]
Would the following solution be valid?

2 situations when the given statement is factored will be
1. x(x+12)(x-2)>0
2. x(x+12)(x-2)<0

Now in both cases x can't be 0. Thus in both situations X is either positive or negative.

For statement 1 : if x is positive it has to be greater than or equal to 3 : which has no solutions in the given parameters
if x is negative it has to be greater than or equal to -11: -6,-5,-4,-3,-2,-1 (6 solutions)

For statement 2 : if x is positive it has to be lesser than or equal to 1: 1 (One solution)
if x is negative it has to be lesser than or equal to -13: -6,-5,-4,-3,-2,-1(same 6 solutions as statement 1)

Thus the different solutions are -6,-5,-4,-3,-2,-1 and 1 (Total 7)

Thus Answer C
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Re: If x is any integer from -6 to 2 inclusive, how many [#permalink]
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Re: If x is any integer from -6 to 2 inclusive, how many [#permalink]
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