Help plzzz someone solve it i need help

A)

B) Closure property means that a subtraction of polynomials results in another polynomial

Step-by-step explanation:

A) is a fourth-degree polynomial (the greatest exponent of x is 4) with two terms ( and 5x) in standard form (degree drops from left to right, and no exponent of x is repeated, like in x² + 3x²)

B) Example:

4x³ - 2x + 3 - (x³ + x²) =

=  4x³ - x³ - 2x + 3 - x² =

= 3x³ - x² - 2x + 3