is (x^7)(y^2)(z^3)>0?

[bhumika.k.shah]

is (x^7)(y^2)(z^3)>0?

Statement I .yz<0
Statement II . xz>0

OA C

should i not consider the value of y^2 as it will always be positive??

[ajith]

is (x^7)(y^2)(z^3)>0?

Statement I .yz<0
Statement II . xz>0

OA C

should i not consider the value of y^2 as it will always be positive??

y^2 is always positive

so is z^2 and x^6

So the question becomes

xz>0?

Which can be solved using Statement 2 alone

(and my answer differs with OA)

[Assumption: x,y,z are real]

[VikingWarrior]

is (x^7)(y^2)(z^3)>0?

Statement I .yz<0
Statement II . xz>0

1. yz<0 so either
a. y - , z+ thus true but if
b. y+, z- it is not true unless x is -

2. xz >0 so either
a. x +, z + thus true since y^2 must be +
b. x - , z - still true since x^7 is - and z^3 is -

For me answer is B

[VikingWarrior]

Ajith, you are a champ at Math man!

[ajith]

Ajith, you are a champ at Math man!

Thanks a ton

[Brent@GMATPrepNow]

is (x^7)(y^2)(z^3)>0?
Statement I .yz<0
Statement II . xz>0
OA C
should i not consider the value of y^2 as it will always be positive??

The statement that y^2 is always positive isn't entirely correct.
We might say that y^2 is usually positive. However, y^2 is not positive when y=0.

So, statement (2) doesn't help rule out the possibility that y might equal 0.
Statement (1) tells us that y does not equal zero.

So, we need both statements to answer the question.
Answer = C

[VikingWarrior]

Excellent point Brent, thanks for pointing it out.
But now shouldn't the answer be E?

1. yz<0 so either
a. y - , z+ thus true but if
b. y+, z- it is not true unless x is -

2. xz >0 so either
a. x +, z + thus true since y^2 must be +
b. x - , z - still true since x^7 is - and z^3 is -

consider situation 1b and 2a then it is negative!

[ajith]

The statement that y^2 is always positive isn't entirely correct.
We might say that y^2 is usually positive. However, y^2 is not positive when y=0.

So, statement (2) doesn't help rule out the possibility that y might equal 0.
Statement (1) tells us that y does not equal zero.

So, we need both statements to answer the question.
Answer = C

Thanks for pointing out the mistake

[VikingWarrior]

sorry, of course I am wrong 1b and 2 a are mutually exclusive! Answer IS C

[bhumika.k.shah]

No,
u will require both statements which will finally conclude that y is not equal to zero.

Regards,
Bhumika

Excellent point Brent, thanks for pointing it out.
But now shouldn't the answer be E?

1. yz<0 so either
a. y - , z+ thus true but if
b. y+, z- it is not true unless x is -

2. xz >0 so either
a. x +, z + thus true since y^2 must be +
b. x - , z - still true since x^7 is - and z^3 is -

consider situation 1b and 2a then it is negative!

[bhumika.k.shah]

So now that we know the answer Option is C...Ajith is this question of urs really valid ?
I wanna know what the main question is been asked here !

Is the question that u derived correct ???

is (x^7)(y^2)(z^3)>0?

Statement I .yz<0
Statement II . xz>0

OA C

should i not consider the value of y^2 as it will always be positive??

y^2 is always positive

so is z^2 and x^6

So the question becomes

xz>0?

Which can be solved using Statement 2 alone

(and my answer differs with OA)

[Assumption: x,y,z are real]