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

• Oct 28th 2012, 12:51 PM
firefox0903
Can someone help me with this pre-Calculus question?
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)
• Oct 28th 2012, 12:58 PM
MarkFL
Re: Can someone help me with this pre-Calculus question?
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\$.
• Oct 28th 2012, 01:03 PM
skeeter
Re: Can someone help me with this pre-Calculus question?
post problems in the precalculus forum please.
• Oct 28th 2012, 01:17 PM
firefox0903
Re: Can someone help me with this pre-Calculus question?
so if f(d)=0 then then the new f(x) is 2x^2+31x+5??
• Oct 28th 2012, 03:08 PM
MarkFL
Re: Can someone help me with this pre-Calculus question?
No, that doesn't mean to let d = 0, that means when x = d, f(x) = 0.