Mathematics

Mathematics

Problem

Consider g(x)=2x3+x2−13x+6g(x)=2x^{3}+x^{2}-13x+6. If x−2x-2 is a factor of g(x)g(x), which of the following represents the complete factorisation of g(x)g(x) over real numbers? a) (x−2)(2x+1)(x−3)(x-2)(2x+1)(x-3) b) (x+2)(2x−1)(x−3)(x+2)(2x-1)(x-3) c) (x−2)(2x−1)(x+3)(x-2)(2x-1)(x+3) d) (x−2)(x−1)(2x+3)(x-2)(x-1)(2x+3)
Intuitive explanation

Since x−2x-2 is a factor, you know that g(2)=0g(2)=0, which means you can divide g(x)g(x) by (x−2)(x-2) using polynomial long division or synthetic division to find the quotient. That quotient will be a quadratic, which you can then factor by finding its roots or recognizing a pattern. The key is to reduce the cubic to a simpler problem you already know how to solve.

Intuitive explanation

Since x−2x-2 is a factor, you know that g(2)=0g(2)=0, which means you can divide g(x)g(x) by (x−2)(x-2) using polynomial long division or synthetic division to find the quotient. That quotient will be a quadratic, which you can then factor by finding its roots or recognizing a pattern. The key is to reduce the cubic to a simpler problem you already know how to solve.

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