Given:
The leading coefficient of a polynomial is 8.
Polynomial roots are 1 and 2.
The graph passes through the point (4,5).
To find:
The 3rd root and the equation of the polynomial.
Solution:
The factor form of a polynomial is:
Where, a is a constant and 
are the roots of the polynomial.
Polynomial roots are 1 and 2. So, 
and 
are the factors of the polynomial.
Let the third root of the polynomial by c, then 
is a factor of the polynomial.
The leading coefficient of a polynomial is 8. So, a=8 and the equation of the polynomial is:
The graph passes through the point (4,5). Putting 
, we get
Divide both sides by 48.
Therefore, the 3rd root on the polynomial is 
.
