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if AB=A and BA=B then which is correct a) A^2=A b) B^2=B c)A=I d) B=I? chapter matrices

if AB=A and BA=B then  which is correct a) A^2=A   b) B^2=B   c)A=I   d) B=I? chapter matrices 

Grade:12th pass

5 Answers

maheshchary
37 Points
7 years ago
C
Nikhil Upadhyay
171 Points
7 years ago
Both options (a) and (b) are correct .A2=A & B2=B.
rajnish kumar
21 Points
7 years ago
Nikhil Upadhyay but why C and D not correct??? if we multiply both side by  A inverse.... we will get A=I.  ???
Nikhil Upadhyay
171 Points
7 years ago
Look options a)   and b) are correct showing that options c and d are also correct.see below for explaination.
A2=A--------->A.A=A------------->A=A-1.A(taking one of the A to right side so it became A inverse)
But (A-1.A=I) Therefore A=I.Similarily B=I.Thus option a and b are correct implementing options c and d.
rajnish kumar
21 Points
7 years ago
i am getting you. but  in the book answer is only a and b. so i am confused.

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