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If s^4*v^3*x^7 < 0 , is svx < 0? 1) v < 0 2) x > [#permalink]
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22 Jan 2010, 04:33
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If \(s^4*v^3*x^7 < 0\), is \(svx < 0?\) 1) \(v < 0\) 2) \(x > 0\)
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Re: Power [#permalink]
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22 Jan 2010, 05:40
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Rules to consider: 1. A negative number to the power of an odd number is always negative. 2 .A negative number to the power of an even number is always positive. 3. A negative times a negative is always positive. 4. A negative times a positive is always negative.
You have s^4 which is an even power and will always be positive. V^3 will be negative if V is negative. V^3 will be negative if V is negative. X^7 will be positive if X is positive. X^7 will be positive if X is positive.
So, solution one, v<0: We know s^4 is positive. We know v^3 is negative since v<0 and it is an odd power. But, x could be either positive or negative, meaning x^7 could be either. Since we know s^4*v^3*x^7 is negative, we have: (+)*()*(?) = () Therefore we can determine x^7 is positive, and thus x is positive. HOWEVER, don't get tripped up on 'S'  just because s^4 is positive, s could be positive or negative. s*v*x = (?)*()*(+) is < 0 if s is positive and > 0 if s is negative. Therefore, one alone is not enough.
Likewise, with solution two, x>0: We have s^4*v^3*x^7 < 0 So, (+)*(?)*(+) = () Therefore, v^3 must be negative. Thus, v < 0. HOWEVER, don't get tripped up on 'S'  just because s^4 is positive, s could be positive or negative. s*v*x = (?)*()*(+) is < 0 if s is positive and > 0 if s is negative. Therefore, two alone is not enough.
Put them together: V<0 X>0 S^4*V^3*X^7 = (+)*()*(+)<0, which they already tell you, so this gives you no new information. S could still be positive or negative (since it is an even power).
So, is s*v*x < 0? We can't determine this, because s could be negative or positive.
So, your answer is e  neither solution alone nor together.
Confusing?



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Re: Power [#permalink]
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22 Jan 2010, 06:09
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rahulms wrote: If \(s^4*v^3*x^7 < 0\), is \(svx < 0?\)
1) \(v < 0\) 2) \(x > 0\) \(s^4*v^3*x^7 < 0\) says V and X are of different sign and S could be positive or negtive. to find \(svx < 0?\) Yes/No question type V*X= negative and S=positive will give answer Yes V*X= negative and S=negative will give answer No Question stem = find whether S is positive or negative 1. V is negative but it doesn't say anything about S; Not SUFF 2. X is positive but it doesn't say anything about S; Not SUFF 1 & 2 Again no clue whether S is positive or negative; Not SUFF Answer E



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Re: Power [#permalink]
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09 Feb 2010, 14:46
If , S^4*v^3*x^7<0, is svx<0?
1) v<0 2) x>0
sol: consider only stmt 1, where v is negative but S is always positive, becoz of its even power, but X can be postive or negative, becoz of its odd power. so svx can greater or lesser than zero. finally stmt 1 alone is not suffcient to answer now consider stmt 2, where again S is always positive and V can be positive or negative, becoz of its odd power, and x is always postive. so, SVX can again greater or lesser than zero. finally stmt 2 alone is not sufficient to answer
but combining both stmt 1 and stmt 2, S is always positive, V is always negative, and X is always positive, now SVX < 0 , can be answered, both stmts combinely are sufficient to answer.
OA is C



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Re: Power [#permalink]
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09 Feb 2010, 19:40
pradeepsrilatha wrote: If , S^4*v^3*x^7<0, is svx<0?
1) v<0 2) x>0
sol: consider only stmt 1, where v is negative but S is always positive, becoz of its even power, but X can be postive or negative, becoz of its odd power. so svx can greater or lesser than zero. finally stmt 1 alone is not suffcient to answer now consider stmt 2, where again S is always positive and V can be positive or negative, becoz of its odd power, and x is always postive. so, SVX can again greater or lesser than zero. finally stmt 2 alone is not sufficient to answer
but combining both stmt 1 and stmt 2, S is always positive, V is always negative, and X is always positive, now SVX < 0 , can be answered, both stmts combinely are sufficient to answer.
OA is C S is not always positive but S^2 is always positive E is the answer



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Re: Power [#permalink]
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10 Feb 2010, 16:58
i do not understand what is the need in solving this the value of s is not given , so that means s can be 0 and s^2 will also be 0 so, E
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If s^4*v^3*x^7 < 0 , is svx < 0? 1) v < 0 2) x > [#permalink]
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10 Feb 2010, 17:11



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Re: Power [#permalink]
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10 Feb 2010, 17:48
oops , yes ,missed that , we do need to solve this
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Re: If s^4*v^3*x^7 < 0 , is svx < 0? 1) v < 0 2) x > [#permalink]
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23 Sep 2016, 09:49
Definitely agree with E being the answer.
1) v<0 > means x>0, but we still don't know value of s, thus INSUFFICIENT
2) x>0 > means v<0, but we still don't know value of s, thus INSUFFICIENT
A,B,D eliminated...
(1) + (2) > Still INSUFFICIENT as we don't know value of s  it can still be either positive or negative
D eliminated...



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Re: If s^4*v^3*x^7 < 0 , is svx < 0? 1) v < 0 2) x > [#permalink]
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28 Nov 2017, 22:08
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Re: If s^4*v^3*x^7 < 0 , is svx < 0? 1) v < 0 2) x >
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