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?(Angry)

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- Oct 28th 2012, 01:29 PMfirefox0903Can 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?(Angry)

- Oct 28th 2012, 03:14 PMMarkFLRe: Can someone help me with this pre-Calculus question?
Hint: $\displaystyle f(d)=2(d)^2-d(d)+(31-d^2)(d)+5=2d^2-d^2+31d-d^2+5=0$

Write in standard form:

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

Now, use the rational roots theorem to see if this cubic has any integral roots. - Oct 30th 2012, 09:07 PMSalahuddin559Re: 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 - Oct 30th 2012, 09:24 PMMarkFLRe: 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.