Q:若V為一向量空間，W為V的子集且為一向量空間，則W為V的一子空間。
ANS:(X)
No. This should make sure that the field and the operations of V and
W are the same. Otherwise for example, V = R and W = Q respectly.
Then W is a vector space over Q but not a space over R and so not
a subspace of V .
請問W為V的子集
為何W跟V 卻可能不是佈於同一體??
假設V佈於R 子集W不也都佈於R嗎??