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by resilient » Sun Feb 17, 2008 11:25 pm
If 2xy + z = 9, what is the value of the positive integer z?

(1) xyz – z^2 = 0

(2) x + y – 3z = -5


qa is a i chose C
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by its_me07 » Mon Feb 18, 2008 4:18 am
OA is a

St 1 gives xyz=z^2 and putting this value in Q stem gives
2xy+z=9
2xyz + z^2=9z
2z^2+z^2=9z
3z^2=9z
z=3

ST 2...........InSUFF as we don have any values for x and y.
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by its_me07 » Mon Feb 18, 2008 4:25 am
OA is a

St 1 gives xyz=z^2 and putting this value in Q stem gives
2xy+z=9
2xyz + z^2=9z
2z^2+z^2=9z
3z^2=9z
z=3

ST 2...........InSUFF as we don have any values for x and y.
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by tar.goyal » Tue Feb 26, 2008 2:16 am
Well the equation in the question simplifies to:
xy=9-z/2

if we substitute this value of xy in the equation given in (1) :
xyz - z^2=0
z(xy-z^2)=0
z((9-z)/2-z^2)=0
This simplifies to :
-3z(z-3)=0
now we get two values of z = 0, 3
Since it is given in the question that z is a positive int, the value of z could only b 3.
so (I) is SUFF

(II) is INSUFF as we are not given with the values of x and y.

So the ans shld b A
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