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If the polynomial x^3+2x^2+ax+b has factors …

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If the polynomial x^3+2x^2+ax+b has factors x+1 and x-1, find the value of a and b

  • 1 answers

Payal Singh 8 years, 5 months ago

p(x) = {tex}x^3+2x^2+ax+b{/tex}

As x+1 is factor of p(x)

Then

p(-1)=0

=> {tex}(-1)^3+2(-1)^2+a(-1)+b=0{/tex}

{tex}=>-1+2-a+b=0{/tex}

=> b-a = -1 .......(1)

Also x-1 is factor of p(x)

p(1)=0

=> {tex}(1)^3+2(1)^2+a(1)+b=0{/tex}

=> 1+2+a+b=0

=> b+a=-3 .......(2)

Adding (1) and (2), we get

=> 2b= -4

=> b =-2

From (2)

=> 2+a=-3

=> a = -5

 

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