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Mathematics 7 Online
MARC:

Factorise each of the following polynomials.

MARC:

\(2x^{3}-3x^{2}+1\)

MARC:

I got the answer correct but not sure whether my working is right...

MARC:

Here is my working: Let P(x)=\(2x^{3}-3x^{2}+1\) The constant term for P(x)=\(2x^{2}-3x^{2}+1\) is 1. Hence,if (x-a) were to be a factor of 1,a=\(\pm1\) If x=1,P(1)=\(2(1)^{3}-3(1)^{2}+1=0\) Hence,(x-1) is a factor of P(x). If x=-1,P(-1)=\(2(-1)^{3}-3(-1)^{2}+1=-4\neq0\) Hence,(x+1) is not a factor of P(x). Hence,by factor theorem,(x-1) is a factor of P(x).

MARC:

Using the long division method,the quotient i got is \(2x^{2}-x-1\)

MARC:

Therefore,P(x)=\(2x^{2}-3x^{2}+1\) =\((x-1)(2x^{2}-x-1)\) =\((x-1)(x-1)(2x+1)\) =\((x-1)^{2}(2x+1)\)

MARC:

@Zepdrix

Zepdrix:

Hmm I've never heard of the factor theorem before, but your work looks good! :) `If the coefficients add up to zero,` `then x=1 is a root of the polynomial,` `and x-1 must be a factor.` And then from there you applied long division? Yayyy good job

MARC:

Yes,i tried applying long division since i don't hv any other methods to factorise it completely.

MARC:

Thank you! @Zepdrix

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