19.2    a) Determinant[{{2,2,2},{2,2,2},{2,2,2}}]
        b) Determinant[{{1,2,3},{4,5,6},{1,3,4}}] - Determinant[{{4,5,6},{1,2,3},{1,3,4}}]
        c) Determinant[{{2,2,3},{4,4,6},{5,5,5}}]
        d) Determinant[{{2,3,4},{4,2,3},{4,3,2}}] - Determinant[{{2,4,4},{3,2,3},{4,3,2}}]
        e) Determinant[{{2,3,5},{3,0,0},{5,0,0}}]
        f) Determinant[{{10,-3},{-4,2}}] - 2*Determinant[{{5,-2},{-3,1}}]

19.6    b) Determinant[{{0,0,0,-5},{0,-1,0,0},{0,0,1,2},{3,0,2,0}}]
        c) Determinant[{{2,-5,4,3},{3,-4,7,5},{4,-9,8,5},{-3,2,-5,3}}]

19.7    a) Determinant[{{1,1,3,4},{2,0,0,8},{3,0,0,2},{4,4,7,5}}]
        b) Determinant[{{5,2,3,4},{0,-1,1,0},{2,5,0,1},{0,7,3,0}}]
        d) Determinant[{{3,-3,-2,-5},{2,5,4,6},{5,5,8,7},{4,4,5,6}}]
        g) Determinant[{{128,256,384,512},{1/4,3/8,1/8,1/4},{1/64,1/64,1/64,-1/64},{2,0,-4,-12}}]

19.8    a) Determinant[{{7,3,4},{1,2,1},{3,0,2}}]
        f) Determinant[{{1,1,1,1},{1,2,1,2},{1,1,2,3},{1,1,1,4}}]
        g) Determinant[{{2,1,3,4,2},{6,2,1,4,1},{6,3,9,12,6},{2,1,3,4,1},{1,4,2,1,1}}]
        m) Determinant[{{1001,1002,1003,1004},{1002,1003,1001,1002},{1001,1001,1001,999},{1001,1000,998,999}}]

19.11	Eigenvalues[{{1,3,4,12},{1/2,0,0,0},{0,1/4,0,0},{0,0,2/3,0}}]
	solve -x+3y+4z+12u =0, 1/2x-2y=0, 1/4y-2z=0, z-3u=0