See Linear subspace. is a subspace because these three conditions hold:
See Linear subspace. is a subspace because these three conditions hold:
To show is a subspace, you must show the three conditions listed in the linear subspace link hold.
The first condition, for example, is To show this holds, you note as I did that so the vector satisfies the equation defining , which is . Notice the hint says use a matrix equation.
The other two conditions are done similarly.