Find an orthonormal basis B for R2 in which the matrix of the operator T(z, y, z)=(-2x+y+z, x-2y+z, x+y-2z) is diagonal, 1967 67. Find an orthonormal basis for C in which the matrix of T(1,2)=(2x1 + (1 - i) x2, (1+i)x1+3x2) is diagonal.