The trinomial expression is .

The trinomial compare to general trinomial expression: ,So x = z, b = 18, c = 40.

To find two numbers with a sum of 18 and a product of 40.

This trinomial list of the factors of 40, and look for the pair of factors is a sum of 18.

The correct factors are 2 and 20.

To factor trinomials of the form , find two integers, m and n, with a sum equal to b and a product equal to c.

Then write  as (x + m)(x + n).

  (Product of two different sings is negative)

Check:

To check the solution by multiply the two factors.

  (Using FOIL method)

                   (Product of two different sings is negative)

Combine like terms using distributive property: ac bc = (a b)c.

The solution is "true".

The solution is .