Help understanding Replacement theorem Friedberg
Hello everyone, im having trouble understanding the Replacement Theorem proof outline in Friedberg Linear Algebra 4th pg 45.
Theorem 1.10 (Replacement Theorem)
Let
be a vector space that is generated by a set
containing exactly
vectors, and let
be a linearly independent subset of
containing exactly vectors. Then
and there exists a subset
of
containing exactly
vectors such that
generates 
The proof is by induction on
, I skipped the base case
.
Inductive step
Let
, be a linearly independent subset of
consisting of
vectors. Then
is linearly independent, and so we may apply the induction hypothesis to conclude that
and that theres is a subset
of
such that
generates
. Thus there exist scalars
such that
.
Note that
, lest
be a linear combination of
which contradicts the assumption that L is linearly independent.
I am having trouble understanding why does
.
Could someone give me a hint so I can understand. Thanks!
Edit: Is it beacause the induction hypothesis gives us
and and since
has an extra vector means that they cannot be equal?
Re: Help understanding Replacement theorem Friedberg
Since m <= n, the only choices are m < n and m = n. If m = n, then from

we have

i.e., L is not linearly independent, contrary to the assumption.
Re: Help understanding Replacement theorem Friedberg
Thanks, I over looked n-m=0