Question 1145341
let the one variable be x.
the linear equation can have the highest degree of the variable equal to 1.
it can be at most a binomial, composed of the variable and a constant.
an example would be 5x + 3.
to make it a trinomial, you would have to add another term, but that can't be done because, when you combine like terms, you're back to two terms which is a binomial.
an example:
5x + 3 + 7x - 4
combine like terms and you get 12x - 1 which is a binomial.
no matter how many time you try to add or subtract like terms, the simplified version of the expression always collapses to two terms.


here's a similar answer from the web.
<a href = "https://www.answers.com/Q/Why_is_it_impossible_to_have_a_linear_trinomial_with_one_variable" target = "_blank">https://www.answers.com/Q/Why_is_it_impossible_to_have_a_linear_trinomial_with_one_variable</a>