If the side length of square ABCD is 1 and point P moves on line AC, then the value range of AP & nbsp; · & nbsp; (Pb + PD) is______ .

If the side length of square ABCD is 1 and point P moves on line AC, then the value range of AP & nbsp; · & nbsp; (Pb + PD) is______ .

Let a (0,0), B (1,0), C (1,1), D (0,1) set P (x, x) (0 ≤ x ≤ 1) AP = (x, x), & nbsp; Pb = (1 − x, − x), PD = (− x, 1 − x) | AP · & nbsp; (Pb + PD) = 2x (1-2x) = − 4 (x − 14) 2 + 14 & nbsp