Question

why know =12 is neglected

Answer 1

Hi soumiya :
 here is your answer 
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  in this solution k=12 in neglected bcz if you put k=12 in quadratic equ it will not satisfy it.
lets see 
puttin k=12 in (k-12)x2 + 2(k-12)x +2=0
   (12-12)x2 + 2(12-12)x +2=0        
   0+0+2=0
2=0
 which is not possible 
thats why here k=12 is neglected!!!
hope  u understand!