\(a^{4}\)+\(b^{4}\)+\(c^{4}\)-2\(b^{2}\)\(c^{2}\)-2\(c^{2}\)\(a^{2}\)-2\(a^{2}\)\(b^{2}\)
の因数分解を教えてください。
★完全解答希望★
\(a^{4}\)+\(b^{4}\)+\(c^{4}\)-2\(b^{2}\)\(c^{2}\)-2\(c^{2}\)\(a^{2}\)-2\(a^{2}\)\(b^{2}\)
の因数分解を教えてください。
★完全解答希望★
丁寧に書いてみます(=^・^=)
[解]
\(a^{4}\)+\(b^{4}\)+\(c^{4}\)-2\(b^{2}\)\(c^{2}\)-2\(c^{2}\)\(a^{2}\)-2\(a^{2}\)\(b^{2}\)
=\(a^{4}\)-2(\(b^{2}\)+\(c^{2}\))\(a^{2}\)+\(b^{4}\)+\(c^{4}\)-2\(b^{2}\)\(c^{2}\)
=\(a^{4}\)-2(\(b^{2}\)+\(c^{2}\))\(a^{2}\)+(\(b^{2}\)-\(c^{2}\)\()^{2}\)
=\(a^{4}\)+2(\(b^{2}\)-\(c^{2}\))\(a^{2}\)+(\(b^{2}\)-\(c^{2}\)\()^{2}\)-4\(a^{2}\)\(b^{2}\)
=(\(a^{2}\)+\(b^{2}\)-\(c^{2}\)\()^{2}\)-4\(a^{2}\)\(b^{2}\)
=(\(a^{2}\)+2ab+\(b^{2}\)-\(c^{2}\))(\(a^{2}\)-2ab+\(b^{2}\)-\(c^{2}\))
={(a+b\()^{2}\)-\(c^{2}\)}{(a-b\()^{2}\)-\(c^{2}\)}
=(a+b+c)(a+b-c)(a-b+c)(a-b-c)
ここでやめて十分ですが、対称性を重んずるなら以下
=-(a+b+c)(a+b-c)(a-b+c)(-a+b+c)
または
=(a+b+c)(-a-b+c)(-a+b-c)(a-b-c)
与式=\(a^{4}\)-2(\(b^{2}\)+\(c^{2}\))\(a^{2}\)+\(b^{4}\)+\(c^{4}\)-2\(b^{2}\)\(c^{2}\)
=\(a^{4}\)-2(\(b^{2}\)+\(c^{2}\))+(\(b^{2}\)-\(c^{2}\)\()^{2}\)
={\(a^{2}\)-(\(b^{2}\)+\(c^{2}\))}^2-(\(b^{2}\)+\(c^{2}\)\()^{2}\)+(\(b^{2}\)-\(c^{2}\)\()^{2}\)
=(\(a^{2}\)-\(b^{2}\)-\(c^{2}\)\()^{2}\)-4\(b^{2}\)\(c^{2}\)
={(\(a^{2}\)-\(b^{2}\)-\(c^{2}\))+2bc}{(\(a^{2}\)-\(b^{2}\)-\(c^{2}\))-2bc}
={\(a^{2}\)-(b-c\()^{2}\)}{\(a^{2}\)-(b+c\()^{2}\)}
={a-(b-c)}{a+(b-c)}{a-(b+c)}{a+(b+c)}
=(a-b+c)(a+b-c)(a-b-c)(a+b+c)・・・(答)