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OG 11 QNO 56 FIND XY

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by georgy » Sun May 10, 2009 11:42 pm
GUYS,.
PL HELP ME OUT.

WHAT IS THE VALUE OF XY?
(1) Y = X + 1
(2) Y = X^2 + 1

WHEN WE SOLVE, WE ARRIVE AT X^3=X^2 OR X^2 = X.
FROM HERE OG GIVES A DIFFERENT EXPLANATION
IT SAYS SINCE X^2 =X , X=1 OR X=0 .
MY EXPLANATION WOULD BE SINCE X^2 = X , X=1 ONLY. ( BY CANCELLING OUT THE COMMON X)

OG'S ANSWER SEEMS LOGICAL,BUT HOW CAN I ARRIVE AT THE SAME CONCLUSION USING MY METHOD.

THANKS IN ADVANCE
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Source: — Data Sufficiency |

by Sunshine85 » Mon May 11, 2009 12:30 am
x^2 = x, you cannot cancel x because x^2 has 2 solutons to it.

so u have to equate the equation to zero and find out the roots.

Hope my expl is clear?

or try out this way.

Zero ^ 2 = Zero --- Zero * Zero = Zero

Cancel zero on both sides..

Zero = one ( as per given logic) which is not true.

You can cancel out x on both sides only if zero is not a root of x.
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thanks

by georgy » Mon May 11, 2009 1:31 am
thanks buddy...u r my sunshine !
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