Question 155388
Remember, not every trinomial is factorable.  If not factorable, they are called "prime".
Factor:
{{{x^2-16x+51}}} Look at the constant term, 51, its factors are  3 and 17.
Now, can you ever get the middle coefficient of -16 by adding or subtracting 3 and 17?
3+17 = 20
-3+(-17) = -20
3-17 = -14
-3-(-17) = 14
The answer is no!
So the trinomial is, therefore, prime!