I am getting D) . OA please.
Will post the explanation if its right.
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DS Plz. help
Source: Beat The GMAT — Data Sufficiency |
Come on! Lets hear it. Don't be shy. Nobody, but me, will would make fun of you if you did something wrongcramya wrote:I am getting D) . OA please.
Will post the explanation if its right.
Let me try:
X^n = X^(n+2)
X^n=X^n X ^2
So X^2 = 1 .......... x ( -1, +1)
question is whether x > 0
( I feel like I am missing something here but..)
Statement I)
X^2-X-2=0 ........x(-1, 2)
So should we say, yes it is sufficient because one of the roots is -1 ?
Statement II)
2X-X^5 < 0
X(2-X^4) < 0
So X <0 or X > 2^(1/4)
oh well -1 and + 1 can be part of these two solutions but...it is not certain and it seems to be insufficient to me
( My confusion still goes on)
I would say A, and I am not 100 % sure
Any more takers ?
Cramya, do I miss something in Statement II ?
LGTCH
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"DON'T LET ANYONE STEAL YOUR DREAM!"
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"DON'T LET ANYONE STEAL YOUR DREAM!"
Logitech,
I still stick to D) with x=-1. However I did not consider fractions when choosing values for x(as it would have got too complicated).This is where I think if I missed something....
I am not sure if 1 will satisfy statement II like u said since its given 2x<x^5 with x=1
2(1) > 1 ^ 5
I am sure the experts here can provide us with a generic approach to this problem.
Regards,
Cramya
I still stick to D) with x=-1. However I did not consider fractions when choosing values for x(as it would have got too complicated).This is where I think if I missed something....
I am not sure if 1 will satisfy statement II like u said since its given 2x<x^5 with x=1
2(1) > 1 ^ 5
I am sure the experts here can provide us with a generic approach to this problem.
Regards,
Cramya
x^n = x^(n+2)
x^n = x^n x^2
Divide by x^n
1 = x^2
x= +1 or -1
Now -1 is the only value that satisfy both statements when evaluating it independently.
Hence D)
Hope I have not missed something here.
Comments, suggestions or positive critique welcome!
x^n = x^n x^2
Divide by x^n
1 = x^2
x= +1 or -1
Now -1 is the only value that satisfy both statements when evaluating it independently.
Hence D)
Hope I have not missed something here.
Comments, suggestions or positive critique welcome!
How about 2 ? :!:cramya wrote:x^n = x^(n+2)
x^n = x^n x^2
Divide by x^n
1 = x^2
x= +1 or -1
Now -1 is the only value that satisfy both statements when evaluating it independently.
Hence D)
Hope I have not missed something here.
Comments, suggestions or positive critique welcome!
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Hmm, today is not my day. Well 2 makes both statement valid..but I guess I am confused here. We are only checking two X values right ?cramya wrote:I dont understand. Are u saying x=2?How about 2
-1 and + 1
We can find -1 from statement 1 hmm I think it is D .
You are correct Cramya.
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Let me complete the discussion...logitech wrote:what if n = 0 ?nishanttheone wrote:x^n = x^(n+2) is valid even for x = 0.
Wouldnt it make A the correct answer?
According to the equation given
x^n = x^n+2
It is possible only for 3 values
x=-1,0,1
Now we need to find is x<0?
According to 1.
x^2-x-2=0
we get x=-1 and x=2.
So, x=2 does not satisfy original euantion hence x=-1 which is one of the values which we have from the original equation.
Hence, stmt 1 is suff. Eliminate B,C,E
Now according to 2.
2x<x^5
subsitute values
we will see that only on x=-1 this equation holds true.
Now u may feel that x=-1/2 also satisy this equation but, it will not hold true for the equation given in the question.
hope it helps...
i guess this is where u guys were confused....
For statement 2, I got:
X(2-x^4) < 0
2 OPTIONS: X<0 or 2 < x^4 ---->X= +/- 1.2
So why D is OK?
THANKS.
X(2-x^4) < 0
2 OPTIONS: X<0 or 2 < x^4 ---->X= +/- 1.2
So why D is OK?
THANKS.
Since the only numbers that can be x are -1,0, and 1, we can rephrase this question as....
If x=-1,0,1 is x=1?
statement 1:
when solve for x, x=-1 or 2, therefore the answer is no, x is not equal to 1.
Sufficient
Statement 2:
2x<x^5
If x=-1,0,1, only x=-1 works here, therefore, x is not equal to 1.
Sufficient
(I am so temped to subtract 2x from both sides...but I think that way is wrong, I am not 100% sure)
Please correct me if I made a mistake.
I am pretty sure that you can reword the question as is x=-1? both statements give the same answer too. A very tricky question.
If x=-1,0,1 is x=1?
statement 1:
when solve for x, x=-1 or 2, therefore the answer is no, x is not equal to 1.
Sufficient
Statement 2:
2x<x^5
If x=-1,0,1, only x=-1 works here, therefore, x is not equal to 1.
Sufficient
(I am so temped to subtract 2x from both sides...but I think that way is wrong, I am not 100% sure)
Please correct me if I made a mistake.
I am pretty sure that you can reword the question as is x=-1? both statements give the same answer too. A very tricky question.
