code: public T negative() {
          T A = copy();
          ops.changeSign(A.mat);
          return A;
      }
docs: <p>
  Returns a new matrix whose elements are the negative of 'this' matrix's elements.<br>
  <br>
  b<sub>ij</sub> = -a<sub>ij</sub>
  </p>
  
  @return A matrix that is the negative of the original.