Question

Is X +3 a factor of 2X squared minus 2X -12

Answer 1

Answer: No, x+3 is not a factor of 2x^2-2x-12

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Explanation:

Let p(x) = 2x^2 - 2x - 12

If we divide p(x) over (x-k), then the remainder is p(k). I'm using the remainder theorem. A special case of the remainder theorem is that if p(k) = 0, then x-k is a factor of p(x).

Compare x+3 = x-(-3) to x-k to find that k = -3.

Plug x = -3 into the function

p(x) = 2x^2 - 2x - 12

p(-3) = 2(-3)^2 - 2(-3) - 12

p(-3) = 12

We don't get 0 as a result so x+3 is not a factor of p(x) = 2x^2 - 2x - 12

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Let's see what happens when we factor p(x)

2x^2 - 2x - 12

2(x^2 - x - 6)

2(x - 3)(x + 2)

The factors here are 2, x-3 and x+2