- #1
jamalkoiyess
- 217
- 21
I have encountered this theorem in Serge Lang's linear algebra:
Theorem 3.1. Let F: V --> W be a linear map whose kernel is {O}, then If v1 , ... ,vn are linearly independent elements of V, then F(v1), ... ,F(vn) are linearly independent elements of W.
In the proof he starts with C1F(v1) + C2F(v2) + ... + CnF(vn) and then uses linearity and injectivity to prove that the constants are 0.
I can't see where injectivity is essential, he could have proved it with linearity alone.
He arrives at a point where we have :
F(C1V1 + ... + CnVn) = 0
He uses injectivity here to prove that C1V1 + ... + CnVn = 0 and since v1 ... vn linearly independent, the constants are 0. But that can be also solved by the fact that F is linear.
Theorem 3.1. Let F: V --> W be a linear map whose kernel is {O}, then If v1 , ... ,vn are linearly independent elements of V, then F(v1), ... ,F(vn) are linearly independent elements of W.
In the proof he starts with C1F(v1) + C2F(v2) + ... + CnF(vn) and then uses linearity and injectivity to prove that the constants are 0.
I can't see where injectivity is essential, he could have proved it with linearity alone.
He arrives at a point where we have :
F(C1V1 + ... + CnVn) = 0
He uses injectivity here to prove that C1V1 + ... + CnVn = 0 and since v1 ... vn linearly independent, the constants are 0. But that can be also solved by the fact that F is linear.