Official solution
Let the coordinates of C be (h, k)
So the chord of contact of C w.r.t y = (x-2)2 - 1
\[ \Rightarrow \] y = x2 - 4x + 3 is T = 0
\[y+k \over 2\] = xh + 3 - 2(x+h)
\[ \Rightarrow \] 2(h-2)x - y = -(6-4h-k)
On comparing it with x - y = 3
2 (h -2) = 1 \[ \Rightarrow \] h = \[5 \over 2\]
6 - 4h - k = -3 \[ \Rightarrow \] k = -1
\[ \therefore \] C = (\[5 \over 2\], -1)