Question

Consider the roots of a cubic equation with integral coefficients: −1, −4, and 3. Which choice is a factor of the cubic equation? A) x + 3 B) x − 1 C) x − 4 D) x − 3

Answer 1

D

Explanation:

Lets go case by case.

Given the roots, a factor will be part of the equation if for some of the roots the factor becomes null, i.e., equal to 0.

Is there any root that makes (x+3)=0? No, as it only becomes 0 for x = - 3 and -3 is not a root. So A NO!

Is there a root that makes (x-1)=0? No, as it only becomes 0 for x=1 and 1 is not a root. So B NO!

(x-4)=0 only for x=4, and as 4 is not a root, C NO!

The last, (x-3)=0 if x=3. As 3 is one of the roots, (x-3) is a factor of our equation!

D is the only correct option!