Let bold upper a equals start 3 by 3 matrix 1st row 1st column 1 2nd column negative 2 3rd column negative 2 2nd row 1st column 10 2nd column negative 3 3rd column 1 3rd row 1st column negative 10 2nd column 5 3rd column 1 endmatrix comma bold upper b equals start 3 by 3 matrix 1st row 1st column 9 2nd column 4 3rd column negative 4 2nd row 1st column 4 2nd column 7 3rd column 0 3rd row 1st column negative 4 2nd column 0 3rd column 11 endmatrix period find left-parenthesis bold upper a plus bold upper b right-parenthesis superscript 2.