# Math Help - Can someone help me with this pre-Calculus question?

1. ## Can someone help me with this pre-Calculus question?

If 2x^2-dx+(31-d^2)x+5 has a factor of x - d, what is the value of d if d is an integer?

2. ## Re: Can someone help me with this pre-Calculus question?

Hint: $f(d)=2(d)^2-d(d)+(31-d^2)(d)+5=2d^2-d^2+31d-d^2+5=0$

Write in standard form:

$d^3-d^2-31d-5=0$

Now, use the rational roots theorem to see if this cubic has any integral roots.

3. ## Re: Can someone help me with this pre-Calculus question?

Small missing step: If x-a is a factor of a polynomial P(x), then P(a) = 0 (Remainder theorem).

Salahuddin
Maths online

4. ## Re: Can someone help me with this pre-Calculus question?

That missing step was given in a duplicate post in another forum. I didn't feel it necessary to repeat it, but rather continued the discussion here after he was asked to post in an appropriate forum.