与えられた式 $(x+1)(x^2+x+1)(x^2-x+1)^2$ を展開し、最も簡単な形に整理せよ。代数学多項式の展開因数分解式の整理2025/5/31. 問題の内容与えられた式 (x+1)(x2+x+1)(x2−x+1)2(x+1)(x^2+x+1)(x^2-x+1)^2(x+1)(x2+x+1)(x2−x+1)2 を展開し、最も簡単な形に整理せよ。2. 解き方の手順まず、(x+1)(x2+x+1)(x+1)(x^2+x+1)(x+1)(x2+x+1) の部分を計算します。(x+1)(x2+x+1)=x3+x2+x+x2+x+1=x3+2x2+2x+1(x+1)(x^2+x+1) = x^3+x^2+x+x^2+x+1 = x^3+2x^2+2x+1(x+1)(x2+x+1)=x3+x2+x+x2+x+1=x3+2x2+2x+1 となります。次に、(x2−x+1)2(x^2-x+1)^2(x2−x+1)2 の部分を展開します。(x2−x+1)2=(x2−x+1)(x2−x+1)=x4−x3+x2−x3+x2−x+x2−x+1=x4−2x3+3x2−2x+1(x^2-x+1)^2 = (x^2-x+1)(x^2-x+1) = x^4 - x^3 + x^2 - x^3 + x^2 - x + x^2 - x + 1 = x^4 - 2x^3 + 3x^2 - 2x + 1(x2−x+1)2=(x2−x+1)(x2−x+1)=x4−x3+x2−x3+x2−x+x2−x+1=x4−2x3+3x2−2x+1したがって、与えられた式は(x3+2x2+2x+1)(x4−2x3+3x2−2x+1)(x^3+2x^2+2x+1)(x^4-2x^3+3x^2-2x+1)(x3+2x2+2x+1)(x4−2x3+3x2−2x+1)となります。これを展開します。x3(x4−2x3+3x2−2x+1)=x7−2x6+3x5−2x4+x3x^3(x^4-2x^3+3x^2-2x+1) = x^7 - 2x^6 + 3x^5 - 2x^4 + x^3x3(x4−2x3+3x2−2x+1)=x7−2x6+3x5−2x4+x32x2(x4−2x3+3x2−2x+1)=2x6−4x5+6x4−4x3+2x22x^2(x^4-2x^3+3x^2-2x+1) = 2x^6 - 4x^5 + 6x^4 - 4x^3 + 2x^22x2(x4−2x3+3x2−2x+1)=2x6−4x5+6x4−4x3+2x22x(x4−2x3+3x2−2x+1)=2x5−4x4+6x3−4x2+2x2x(x^4-2x^3+3x^2-2x+1) = 2x^5 - 4x^4 + 6x^3 - 4x^2 + 2x2x(x4−2x3+3x2−2x+1)=2x5−4x4+6x3−4x2+2x1(x4−2x3+3x2−2x+1)=x4−2x3+3x2−2x+11(x^4-2x^3+3x^2-2x+1) = x^4 - 2x^3 + 3x^2 - 2x + 11(x4−2x3+3x2−2x+1)=x4−2x3+3x2−2x+1これらの結果を合計すると、次のようになります。x7−2x6+3x5−2x4+x3x^7 - 2x^6 + 3x^5 - 2x^4 + x^3x7−2x6+3x5−2x4+x3+2x6−4x5+6x4−4x3+2x2+ 2x^6 - 4x^5 + 6x^4 - 4x^3 + 2x^2+2x6−4x5+6x4−4x3+2x2+2x5−4x4+6x3−4x2+2x+ 2x^5 - 4x^4 + 6x^3 - 4x^2 + 2x+2x5−4x4+6x3−4x2+2x+x4−2x3+3x2−2x+1+ x^4 - 2x^3 + 3x^2 - 2x + 1+x4−2x3+3x2−2x+1=x7+(−2+2)x6+(3−4+2)x5+(−2+6−4+1)x4+(1−4+6−2)x3+(2−4+3)x2+(2−2)x+1= x^7 + (-2+2)x^6 + (3-4+2)x^5 + (-2+6-4+1)x^4 + (1-4+6-2)x^3 + (2-4+3)x^2 + (2-2)x + 1=x7+(−2+2)x6+(3−4+2)x5+(−2+6−4+1)x4+(1−4+6−2)x3+(2−4+3)x2+(2−2)x+1=x7+x5+x4+x3+x2+1= x^7 + x^5 + x^4 + x^3 + x^2 + 1=x7+x5+x4+x3+x2+1別解として、x3+1=(x+1)(x2−x+1)x^3+1 = (x+1)(x^2-x+1)x3+1=(x+1)(x2−x+1)の公式を利用します。(x+1)(x2+x+1)(x2−x+1)2=(x+1)(x2−x+1)(x2+x+1)(x2−x+1)=(x3+1)(x4+x2+1)(x+1)(x^2+x+1)(x^2-x+1)^2 = (x+1)(x^2-x+1)(x^2+x+1)(x^2-x+1) = (x^3+1)(x^4+x^2+1)(x+1)(x2+x+1)(x2−x+1)2=(x+1)(x2−x+1)(x2+x+1)(x2−x+1)=(x3+1)(x4+x2+1)(x3+1)(x4+x2+1)=x7+x5+x3+x4+x2+1=x7+x5+x4+x3+x2+1(x^3+1)(x^4+x^2+1) = x^7 + x^5 + x^3 + x^4 + x^2 + 1 = x^7 + x^5 + x^4 + x^3 + x^2 + 1(x3+1)(x4+x2+1)=x7+x5+x3+x4+x2+1=x7+x5+x4+x3+x2+13. 最終的な答えx7+x5+x4+x3+x2+1x^7 + x^5 + x^4 + x^3 + x^2 + 1x7+x5+x4+x3+x2+1