Answer:
Step-by-step explanation:
Trinomial should have only three terms
Binomial should have only two terms
Monomial should have only one term
[tex]21) x^{3} - 2x + 1\\\\22) 3y^{4} - 2y^{3} + 9y -2\\\\23) b^{5} + 2b\\\\24) z^{3} + 5z^{2} + 8z - 25\\\\25) r^{n}[/tex]
