No, the number 5 is not a ploynomial.
Quintinomial
12x2 + 20x - 25 IS a polynomial that factors into (2x + 5)(6x - 5)
The x^5 at the beginning makes the degree of the polynomial 5.
(r + 5)(r + 5)
Quintinomial, is a polynomial with 5 terms
No, the number 5 is not a ploynomial.
2 or 5
It is a polynomial with 5 terms.
Quintinomial
4 and 5 -4 and -8
12x2 + 20x - 25 IS a polynomial that factors into (2x + 5)(6x - 5)
The x^5 at the beginning makes the degree of the polynomial 5.
5
(r + 5)(r + 5)
Sort of... but not entirely. Assuming the polynomial's coefficients are real, the polynomial either has as many real roots as its degree, or an even number less. Thus, a polynomial of degree 4 can have 4, 2, or 0 real roots; while a polynomial of degree 5 has either 5, 3, or 1 real roots. So, polynomial of odd degree (with real coefficients) will always have at least one real root. For a polynomial of even degree, this is not guaranteed. (In case you are interested about the reason for the rule stated above: this is related to the fact that any complex roots in such a polynomial occur in conjugate pairs; for example: if 5 + 2i is a root, then 5 - 2i is also a root.)
The degree of the polynomial 2x + 5 is 1. The highest power of x is x1, i.e. 2x1 + 5x0, hence the designation of first degree.