$A = x^3 + 3x^2 - 2x - 1$, $B = x^2 + 2x - 1$, $C = x - 3$ のとき、$A - (B - C)$ の値を求める問題です。代数学多項式式の計算展開2025/6/41. 問題の内容A=x3+3x2−2x−1A = x^3 + 3x^2 - 2x - 1A=x3+3x2−2x−1, B=x2+2x−1B = x^2 + 2x - 1B=x2+2x−1, C=x−3C = x - 3C=x−3 のとき、A−(B−C)A - (B - C)A−(B−C) の値を求める問題です。2. 解き方の手順まず、B−CB - CB−C を計算します。B−C=(x2+2x−1)−(x−3)=x2+2x−1−x+3=x2+x+2B - C = (x^2 + 2x - 1) - (x - 3) = x^2 + 2x - 1 - x + 3 = x^2 + x + 2B−C=(x2+2x−1)−(x−3)=x2+2x−1−x+3=x2+x+2次に、A−(B−C)A - (B - C)A−(B−C) を計算します。A−(B−C)=(x3+3x2−2x−1)−(x2+x+2)=x3+3x2−2x−1−x2−x−2=x3+(3x2−x2)+(−2x−x)+(−1−2)=x3+2x2−3x−3A - (B - C) = (x^3 + 3x^2 - 2x - 1) - (x^2 + x + 2) = x^3 + 3x^2 - 2x - 1 - x^2 - x - 2 = x^3 + (3x^2 - x^2) + (-2x - x) + (-1 - 2) = x^3 + 2x^2 - 3x - 3A−(B−C)=(x3+3x2−2x−1)−(x2+x+2)=x3+3x2−2x−1−x2−x−2=x3+(3x2−x2)+(−2x−x)+(−1−2)=x3+2x2−3x−33. 最終的な答えx3+2x2−3x−3x^3 + 2x^2 - 3x - 3x3+2x2−3x−3