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Cool goIITian

Joined: 24 Aug 2008
Post: 30
9 Jul 2009 10:47:32 IST
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when u divide (x^4-6x^3+16x^2-25x+10) by (x^2-2x+k) , the remainder is x+a find a and k
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when u divide (x^4-6x^3+16x^2-25x+10) by (x^2-2x+k) , the remainder is x+a find a and k


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SAVVEJ's Avatar

Blazing goIITian

Joined: 4 May 2007
Posts: 697
9 Jul 2009 11:10:27 IST
1 people liked this

by simple division we get remainder as: (2k-9)x + (10- k(8-k))


equating with x+a we get


2k-9 = 1


k= 9/2


10 - k(8-k) = a


putting value of k we get,


a= -23/4 

Siddharth Kothari's Avatar

Blazing goIITian

Joined: 17 May 2009
Posts: 302
9 Jul 2009 11:23:49 IST
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 I agree with SAVVEJ

®µD®A's Avatar

Blazing goIITian

Joined: 12 Apr 2008
Posts: 2717
9 Jul 2009 11:48:40 IST
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Here is a way to cut down the work..

 

x^2 equiv (2x-k) mod (x^2 -2x+k)

 

herefore x^4 - 6x^3+16x^2-25x+10 equiv (2x-k)^2-6(2x^2-kx)+16(2x-k)-25x+10

 

equiv -8x^2+x(2x+7)+(k^2-16k+10) equiv 8(k-2x)+x(2k+7)+(k^2-16k+10)

 

equiv x(2k-9) + (k^2-8k+10)

 

Now equate the co-efficiets ,

 

2k-9=1\\Rightarrow k=5

 

Also,

 

k^2-8k+10=a\\Rightarrow a=-5




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