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Q.

Let x,y,z  be non zero real numbers that satisfy the system of equations:(x2+xy+y2)(y2+yz+z2)(z2+zx+x2)=xyz, and  (x4+x2y2+y4)(y4+y2z2+z4)(z4+z2x2+x4)=x3y3z3  
 

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a

Number of triplets (x,y,z) that satisfy above equations is 3

b

Sum of all possible values of x that satisfy above equation is less than 2

c

Sum of all possible values of y that satisfy above equation is less than 1

d

Number of triplets (x,y,z) that satisfy above equations is less than 4

answer is B, C, D.

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Detailed Solution

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Since  xyz0, we can divide the second relation by the first. Observe that 
 x4+x2y2+y4=(x2+xy+y2)(x2xy+y2).
Holds for any x,y .Thus we get  (x2xy+y2)(y2yz+z2)(z2zx+x2)=x2y2z2
However , for any number x,y, we have x2xy+y2>|xy|
Since     x2y2z2=|xy||yz||zx|,we  get|xy||yz||zx|=(x2xy+y2)(y2yz+z2)(z2zx+x2)0|xy||yz||zx|
This is possible only if
x2xy+y2=|xy|,y2yz+z2=|yz|,z2zx+x2=|zx| ,
Hold simultaneously, However |xy|=±xy. If x2xy+y2=xy,  then x2+y2=0  giving   x=y=0.
Since we are looking for nonzero  x,y,z we conclude that  x2xy+y2=xy which is  same as x=y. .Using the other relations, we also get  y=z and z=x. The first equation  now gives  27x6=x3.This gives  x3=127(since   x0),orx=13.We thus have   x=y=z=13. These also satisfy the second relation, as may be verified

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Let x,y,z  be non zero real numbers that satisfy the system of equations:(x2+xy+y2)(y2+yz+z2)(z2+zx+x2)=xyz, and  (x4+x2y2+y4)(y4+y2z2+z4)(z4+z2x2+x4)=x3y3z3