题目多项式9x2−99x^{2}-99x2−9因式分解的结果是（ ）A.(3x+3)(3x−3)(3x+3)\left(3x-3\right)(3x+3)(3x−3)B.9(x2−1)9(x^{2}-1)9(x2−1)C.9x(x−1)9x\left(x-1\right)9x(x−1)D.9(x+1)((x−1)9\left(x+1\right)(\left(x-1\right)9(x+1)((x−1)知识点：因式分解章节：数学竞赛 / 数与式
