Answer:
Following are the solution to this question:
Step-by-step explanation:
Let X is a set of all polynomials of the third-degree with regular operations.
This set is not a space for a vector since it is not shut down
For instance:
[tex]\to x^3+3x^2+2 \in X \ \ \ and \ \ \ -x^3+2x^2+2x \in X[/tex]
Calculating the sum:
[tex]\to x^3+3x^2+2 + -x^3+2x^2+2x\\\\\to 5x^2+2x+2 \notin X[/tex]
That's why X isn't a space for vectors because X isn't shut down.