value of k

Asked by  | 26th Aug, 2008, 11:00: AM

Expert Answer:

 2x+ px --15 ==0 has  --5  as its root

 so  2 (--5)2 +px -15 ==0 ==>  50 --5p --15 ==0 ==> p  ==7

 the  given quadratic    p( x2  + x) +k   =0   becomes  7(x+x) +k =0 has equal roots

  therefore  b2 --4ac ==0 (  discreminent =0  is the condition for the equal roots)

   72 -- 4 (7) (k) ==0 ==> 49 --28k =0 ==> k ==  49 /28  == 7/4

     k = 7 /4

Answered by  | 26th Aug, 2008, 05:07: PM

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