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Let p(x) be a quadratic polynomial with integer coefficients which has 411 as a root. Compute p(3)p(4).

 May 28, 2019
 #1
avatar+118718 
+2

Hi Lightning  laugh

 

P(x)=ax2+bx+cP(411)=a(411)2+b(411)+c=0Where a,b and c are integersa(411)2+b(411)+c=0a(16+11811)+b(411)+c=0a(27811)+b(411)+c=027a+4b=c(1)8a11b11=08ab=0b=8a(2)sub two into one27a+48a=c5a=cc=5a

 

So the equation becomes

P(x)=ax28ax+5aP(x)=a(x28x+5)

 

Find P(3) and P(4) and do the division.

 

You can finish it   wink

 

(oh, you do need to check my working, I have not done so. )

 May 28, 2019
 #2
avatar+6252 
+2

I'd make this a bit simpler.

 

We can always choose P(x) to be a monic polynomialInteger coefficients means 411 is a root 4+11 is a rootThus we haveP(x)=(x4+11)(x411)=x28x+5

Rom  May 28, 2019
edited by Rom  May 28, 2019
 #3
avatar+118718 
0

That is much nicer Rom :)

Melody  May 28, 2019

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