(i)Prove that if{v1,v2}is linearly dependent, then are multiple of each other, that is, there exists a constant c such that v1 = c v2 or v2=cv1. (ii)P

Trent Carpenter

Trent Carpenter

Answered question

2020-11-06

(i)Prove that ifv1,v2is linearly dependent, then are multiple of each other, that is, there exists a constant c such that v1=cv2 or v2=cv1.
(ii)Prove that the converse of(i) is also true.That is to say, if there exists a constant c such that v1=cv2 or v2=cv1, 1. thenv1,v2is linearly dependent.

Answer & Explanation

hosentak

hosentak

Skilled2020-11-07Added 100 answers

Recall:a limited number of vectors with linear dependence {a1,a2,,an  pf a vector space V over a field F is said to be linearly dependent in V if there exist scalars c1,c2,cn, not all zero, in F such that 
c1a1+c2a2++cnan=0 
θ is the zero element of the vector space V. 
(i)Given{v1,v2}is linearly independent i.e v1,v2 are linearly dependent. Let 0 be the zero element. So there exist scalars c1,c2 such that 
c1v1+c2v2=0
if any one of the scalar is 0,then the other scalar also becomess 0(since the vectors are non zero). 
So for linear dependency both the scalars c1,c2 have to be non-zero.Therefore, 
c1v1+c2v2=0 
c1v1=c2v2 
v1=(c2c1)v2 
v1=cv2 
Similarly, 
c1v1+c2v2=0 
c2v2=c1v1 
v2=(c1c2)v1 
v2=cv1
So it is proved that if {v1,v2} is linearly dependent, then there exist a constant c such that either v1=cv2 or v2=cv1
(ii)Let there exist a constant c not equal to 0 such that either v1=cv2( or v2=cv1)
Then it can be written as, 
v1=cv2 
v1cv2=0 
Hence by the definition of linear dependence we can say that v1,v2 are linearly dependent i.e. 
{v1,v2} is linearly dependent

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