Determine if the statements are true or false. 1. if a and b are n×n matrices and if a is invertible, then aba−1=b. 2. if a and b are real symmetric matrices of size n×n, then (ab)t=ba 3. if a is row equivalent to b, then the systems ax=0 and bx=0 have the same solution. 4. if, for some matrix a and some vectors x and b we have ax=b, then b is a linear combination of the columns of a. 5. different sequences of elementary row operations can lead to different reduced row echelon forms of the same matrix. 6. different sequences of elementary row operations can lead to different row echelon forms of the same matrix. 7. if a and b are invertible n×n matrices, then the inverse of a+b is a−1+b−1.