FOIL 法を用いて $$$\left(x - 1\right)^{2}$$$ を展開せよ

FOIL法を用いて$$$\left(x - 1\right)^{2} = \left(x - 1\right) \left(x - 1\right)$$$を展開してください。

$$$\left({\color{red}\left(x\right)} + {\color{purple}\left(-1\right)}\right) \left({\color{green}\left(x\right)} + {\color{blue}\left(-1\right)}\right) = \underbrace{{\color{red}\left(x\right)} {\color{green}\left(x\right)}}_{\text{最初}} + \underbrace{{\color{red}\left(x\right)} {\color{blue}\left(-1\right)}}_{\text{外側}} + \underbrace{{\color{purple}\left(-1\right)} {\color{green}\left(x\right)}}_{\text{内側}} + \underbrace{{\color{purple}\left(-1\right)} {\color{blue}\left(-1\right)}}_{\text{最後}} = x^{2} - x - x + 1 = x^{2} - 2 x + 1$$$

$$$\left(x - 1\right)^{2} = x^{2} - 2 x + 1$$$A