Determine if the statement is true of false and justify your
     Determine if the statement is true of false, and justify your answer.  If U is a change of basis matrix between bases B_1 and B_2 of R^n, then U must be invertible.  True. Since U = UW^-1 where V has columns given by the basis vectors of B_1, and w has columns given by the basis vectors of B_2, it follows that U is invertible, with U^-1 = WV^-1.  False. Consider B_1 = {[1 1]} and B_2 {[1 0]}.  True. Since U = W^-1V where V has columns given by the basis vectors of B_1, and W has columns given by the basis vectors of B_2, it follows that U is invertible, with U^-1 = V^-1W.  False. Consider B_1 = {[1 1], [1 -1]} and B_2 = {[2 1], [1 1]}. 
  
  Solution
If u is a change of basis matrix between bases B1 and B2 of Rn then u must be invertible:
True, since U = W-1V where v has columns given by the basis vectors of B1 and W has columns given by the basis vectors of B2, it follows that U is invertible with U-1 = v-1 w

