(1) ∣x111x111x∣=x3+1+1−x−x−x=x3−3x+2=(x−1)(x−1)(x+2)=0\begin{vmatrix} x & 1 & 1 \\ 1 & x & 1 \\ 1 & 1 & x \end{vmatrix} = x^3 + 1 + 1 - x - x - x = x^3 - 3x + 2 = (x-1)(x-1)(x+2) = 0x111x111x=x3+1+1−x−x−x=x3−3x+2=(x−1)(x−1)(x+2)=0 とおかばよい よって x = 1, -2 (2) ∣x12213x01∣=x+3x−2x−2=2x−2=0\begin{vmatrix} x & 1 & 2 \\ 2 & 1 & 3 \\ x & 0 & 1 \end{vmatrix} = x + 3x - 2x - 2 = 2x - 2 = 0x2x110231=x+3x−2x−2=2x−2=0 とおかばよい よって x = 1