Let {v1,v2,...,vm } is linearly independent in V and w∈W.
Suppose (v1−w,v2−w,...,vm−w) is Linearly dependent. Then there esists scalars a1,a2,...,am , not all zero such that
a1(v1−w),a2(v2−w)..,am(vm−w)
Rearranging the equation-
a1v1+...+amvm=(a1+...+am)w
If a1+...+am were zero, then the equation above would contradict the linear independence of {v1,v2,...,vm }. Thus a1+....+am=0.
Thus divide both sides of the equation by (a1+...+am) showing that w∈span(v1,v2,..,vm)
⇒dim span(v1−w,v2−w,...,vm−w)≥m−1.
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