(5)(x-a+1)²
={(x-a)+1}²
=(x-a)²+2(x-a)+1
=x²-2ax+a²+2x-2a+1
ーーーーーーーーーーーーーーーーー
(6)(a+b-c)(a-b+c)
={a+(b-c)}{a-(b-c)}
=a²-(b-c)²
=a²-{b²-2bc+b²}
=a²-b²+2bc-b²
五番と6番をといていただけると幸いです。
(5)(x-a+1)²
={(x-a)+1}²
=(x-a)²+2(x-a)+1
=x²-2ax+a²+2x-2a+1
ーーーーーーーーーーーーーーーーー
(6)(a+b-c)(a-b+c)
={a+(b-c)}{a-(b-c)}
=a²-(b-c)²
=a²-{b²-2bc+b²}
=a²-b²+2bc-b²
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