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the question:
the matrix
1 -1
1 -1
has the property that A2 = 0. Is it possible for a nonzero symmetric 2x2 matrix to have this property? Prove your answer.
my work:
for a 2x2 matrix A to be its own inverse, it has to have the form
a b
b a
This squared is
(a2 + b 2) (2ab)
(2ab) (a2 + b2)
(things in parenthesis are their own elements -- it won't save the spaces)
Because there are no real numbers so that a2 + b2 = 0, there is no 2x2 symmetric matrix that has its square equal to the zero vector.
edit: ^^ other than a = 0, and b = 0, which would be a 2x2 zero matrix -- something taken to account in the statement of the question
Is this right? My book doesn't have a solution for this one
the matrix
1 -1
1 -1
has the property that A2 = 0. Is it possible for a nonzero symmetric 2x2 matrix to have this property? Prove your answer.
my work:
for a 2x2 matrix A to be its own inverse, it has to have the form
a b
b a
This squared is
(a2 + b 2) (2ab)
(2ab) (a2 + b2)
(things in parenthesis are their own elements -- it won't save the spaces)
Because there are no real numbers so that a2 + b2 = 0, there is no 2x2 symmetric matrix that has its square equal to the zero vector.
edit: ^^ other than a = 0, and b = 0, which would be a 2x2 zero matrix -- something taken to account in the statement of the question
Is this right? My book doesn't have a solution for this one
Last edited: