How to write a function given through matrices?

Question

Mathematics

Help decipher the function)
How to write it in the usual mathematical form?

Answer 1

an interesting way to write two equations as one
as you have already been told when you multiply a matrix by a vector and you get two equations

Answer 2

(Probably) t is a transposition to row by column. y seems to be a scalar.

y = | x1 x2 | | 5 4 | | x1 |
              |-1 1 | | x2 |

right side (wrong) from right to left [x^t[Ax]]