Verify the assertions from Example 2.18:

  1. A list vv of one vector vVv \in V is linearly independent if and only if v0v \ne 0.
  2. A list of two vectors in VV is linearly independent if and only if neither is a scalar multiple of the other
  3. (1,0,0,0),(0,1,0,0),(0,0,1,0)(1,0,0,0),(0,1,0,0),(0,0,1,0) is linearly independent in F4\mathbf F^4
  4. The list 1,z,,zm1,z,\dots,z^m is linearly independent in P(F)\mathcal P(\mathbf F) for each nonnegative integer mm

  1. If v=0v = 0 then λv=0\lambda v = 0 so not independent, if v0v \ne 0 then λv0\lambda v \ne 0 for all λ0\lambda \ne 0, so independent.
  2. If v1,v2Vv_1,v_2 \in V is dependent then 2.2.1 (a) implies one is a scalar multiple of the other. If v1=λv2v_1 = \lambda v_2 then they're clearly dependent as v1λv2=0v_1 - \lambda v_2 = 0.
  3. Obvious as their sum is (a1,a2,a3,0)(a_1,a_2,a_3,0) which is only zero when a1=a2=a3=0a_1=a_2=a_3=0.
  4. We will show independence by showing that 2.21 (a) does not apply. Suppose
zj=a0+a1z++aj1zj1z^j = a_0 + a_1z + \dots + a_{j-1}z^{j-1}

take the jth derivative to get j!=0j! = 0, contradicting their equality. and since 2.21 does not apply they cannot be dependent.