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I got one more true / false question, this time I need to pick the CORRECT answer:

1. If Y is a non trivial solution of a system Ax=b, then 2Y is also a solution of this system

2. If a system (Ax=b) has 4 equations, 6 unknowns and infinite number of solutions with 2 degrees of freedom, than the rank of A is 2.

3. Let A be a 3X3 matrix so that the system Ax=0 has a solution x=(1 0 3)^t, then A is not invertible.

4. The system Ax=b with m equations and n unknowns (m>n) can not have a single solution.

5. All the statements are wrong

I think that 2 and 4 are wrong. 1 sounds weird, I do not know of trivial / non trivial solution for Ax=b...only for Ax=0...

that leaves me with 3, I am not sure about it, is it correct that if the solution exist, than the system has infinite number of solutions and not just the trivial one ? and in this case, if A is invertible then:

A^-1Ax=A^-10 --> x=0 ?

so 3 is the correct one ?