You can put this solution on YOUR website!
Is the question this:
Is the product of two binomials always a trinomial?
If not, disregard this solution.
(a+b)(a-b)=a^2-ab+ab-b^2=a^2-b^2. This is a binomial. Hence, it is not always true that the product of two binomials is a trinomial.
However, it is true in many other cases: