Consider the polynomials
(ab2+ 3ab+ 8a2) (-5ab2)
Use the polynomials to illustrate the following:
A. Polynomials are closed under addition
B. Polynomials are closed under subtraction
C. Polynomials are closed under multiplication
D. Polynomials are not closed under division

Respuesta :

Hello from MrBillDoesMath!

Answer:

See Discussion for details



Discussion:

Polynomials are closed with respect to an operation if applying that operation to them generates another polynomial

A.   ( ab^2 + 3ab + 8a^2)  +  ( - 5ab^2)  =

       -4ab^2 + 3ab + 8a^2    which is a polynomial


B.   ( ab^2 + 3ab + 8a^2)  -  ( - 5ab^2)  =

       6ab^2 + 3ab + 8a^2    which is a polynomial


C.   ( ab^2 + 3ab + 8a^2)  *  ( - 5ab^2)  =

       -5a^2b^4 - 15a^2b^3 = 40a^3b^2  which is a polynomial


D  ( ab^2 + 3ab + 8a^2)  /  ( - 5ab^2)  =

     -(1/5) + 3(-1/5) (1/b) + 8 ( -1/5)a(1/b^2)

    which is NOT a polynomial because of the (1/b), ( 1/b^2)  terms


Thank you,

MrB