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Q.


The remainder on division of x 3 +2 x 2 +kx+3   by x3   is 21.   Find the quotient and the value of k  .

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a

k=7   and quotient =2 x 2 7x+14  

b

k=9   and quotient = x 2 +5x+6  

c

k=9   and quotient = x 2 5x6  

d

k=7   and quotient =2 x 2 +7x14   

answer is A.

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Detailed Solution


Given that when the polynomial x 3 +2 x 2 +kx+3   is divided by x3   we get the remainder as 21.   We need to find the quotient and value of k.  
We will use the long division method for performing the division.
We have,
Question Image
Quotient is x 2 +5x+(15+k)...(i)  
Remainder is 3+3(15+k)  . But from the question we know that remainder is 21.  
Therefore, we have,
21=3+3(15+k) 21=3+75+3k 18=45+3k 27=3k k= 27 3 k=9  
Equating the value of k   in equation i  , we have,
x 2 +5x+(15+k)= x 2 +5x+(159) x 2 +5x+(15+k)= x 2 +5x+6  
Hence, the value of k   is 9   and the quotient is x 2 +5x+6  .
Therefore, option 1 is correct.
 
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