17.13495 = F k - 1 P k - 1 | k - 1 F k - 1 T +   T k - 1 ⎛ ⎝ x ^ k - 1 ⎞ ⎠ Q k - 1 T k - 1 ⎛ ⎝ x ^ k - 1 ⎞ ⎠ T