a) False. The matrix (1001) is of rank 2 and determinant 1.
b) False. For example, (1001) and (0110) are unitary matrices.
c) False. For example, take U to be the x-axis and V y-axis, both subspaces of R2. Their union includes both (1,0) and (0,1), whose sum, (1,1), is not in the union. Hence, the union is not a vector space.
d) False. According to Rank-Nullity theorem, rank(T)+nullity(T)=dim(R4)=4=6.
e) False. The relation R is not transitive. For example, take L1,L2 and L3 are the lines of equations y=x,y=−x and y=x−1 respectively. We have
L1RL2 and L2RL3, but L1RL3.
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