Answer:
Yes, W is a subspace.
Step-by-step explanation:
Let V be a vector space and W be a subset of V.
W is said to be a subspace of the vector space V if it satisfies the following conditions:
1. W is non-empty.
2. If then
3. If then where k is a scalar.
Solution:
Let
Here, Q denotes the set of rational numbers.
W is non-empty as being a rational number.
Let where a, b, c, d are rational numbers.
as ab + cd is a rational number being the sum and product of rational numbers.
Let and k be a scalar
being the product of rational numbers a and b.
Therefore, W is a subspace as it satisfies all the conditions.