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

#### firefox0903

If 2x2-dx+(31-d2)x+5 has a factor of x - d, what is the value of d if d is an integer? (Crying)

#### MarkFL

Let:

$$\displaystyle f(x)=2x^2-dx+(31-d^2)x+5$$

If $$\displaystyle f(x)$$ has a factor of $$\displaystyle x-d$$ then $$\displaystyle f(d)=0$$.

Hint: use the rational roots theorem on the resulting cubic in $$\displaystyle d$$.

#### skeeter

MHF Helper
post problems in the precalculus forum please.

#### firefox0903

so if f(d)=0 then then the new f(x) is 2x^2+31x+5??

#### MarkFL

No, that doesn't mean to let d = 0, that means when x = d, f(x) = 0.