How do you express this binomial as a trinomial?

Question

I have this equation (x - 9)² and I need to express it as a trinomial and I don't know how

Answer 1

Your first hint here should be that a trinomial often takes the form of ax²+bx+c.

When you square a binomial, such as you are being asked to do here, you do, in fact get a quadratic trinomial. Probably, the only thing you got stuck on here is to write out the squared binomial as two binomials.

Then FOIL the given expression by the usual method:

(x-9)(x-9) = x²-18x+81