Answer:
(a)f(x)=x⁴+3x²
Explanation:
Part A
A polynomial in the fourth degree is any polynomial in which the highest power is 4.
An example of a fourth-degree polynomial with two terms is given below:
[tex]f(x)=x^4+3x^2[/tex]We know that this polynomial is in standard form since it is written in descending powers of x.
Part B
The closure property as it relates to the subtraction of polynomials tells us that when two polynomials are subtracted, one from the other, the result is always a polynomial.
Consider the polynomials, f(x) and g(x) below:
[tex]\begin{gathered} f(x)=x^2-4 \\ g(x)=x^3+8 \end{gathered}[/tex]Subtracting f(x) from g(x):
[tex]\begin{gathered} g(x)-f(x)=\lbrack x^3+8\rbrack-\lbrack x^2-4\rbrack \\ =x^3+8-x^2+4 \\ =x^3-x^2+8-4 \\ =x^3-x^2+4 \end{gathered}[/tex]Observe that the result is also a polynomial, hence the closure property applies.