DS Plz. help

I am getting D) . OA please.

Will post the explanation if its right.

cramya wrote:I am getting D) . OA please.

Will post the explanation if its right.

Come on! Lets hear it. Don't be shy. Nobody, but me, will would make fun of you if you did something wrong

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 ?

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

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!

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!

How about 2 ? :!:

How about 2

I dont understand. Are u saying x=2?

cramya wrote:

How about 2

I dont understand. Are u saying x=2?

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 ?

-1 and + 1

We can find -1 from statement 1 hmm I think it is D .

You are correct Cramya.

OA is D

NICE Discussion !!

Vishu

x^n = x^(n+2) is valid even for x = 0.

Wouldnt it make A the correct answer?

nishanttheone wrote:x^n = x^(n+2) is valid even for x = 0.

Wouldnt it make A the correct answer?

what if n = 0 ?

logitech wrote:

nishanttheone wrote:x^n = x^(n+2) is valid even for x = 0.

Wouldnt it make A the correct answer?

what if n = 0 ?

Let me complete the discussion...
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.

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.