✨ Best Answer ✨
(1)
(x-1)(x-5) = x²-6x+5
(x-2)(x-4) = x²-6x+8
なので (x-1)(x-5)(x-2)(x-4) = {(x-1)(x-5)}{(x-2)(x-4)}
= (x²-6x+5)(x²-6x+8)
(2)
x²-6x+7 = 0 を解くと x = 3±√2 となるので
x = 3+√2 のとき x²-6x+7 = 0
(3)
P = (x²-6x+5)(x²-6x+8) = {(x²-6x+7)-2}{(x²-6x+7)+1} = (0-2)(0+1) = -2