题目下列等式从左到右的变形是因式分解的是（ ）A.12a2b=3a⋅4ab12a^{2}b=3a\cdot 4ab12a2b=3a⋅4abB.(x+3)(x−3)=x2−9\left(x+3\right)\left(x-3\right)=x^{2}-9(x+3)(x−3)=x2−9C.4x2+8x−1=4x(x+2)−14x^{2}+8x-1=4x\left(x+2\right)-14x2+8x−1=4x(x+2)−1D.12ax−12ay=12a(x−y)\dfrac{1}{2}ax-\dfrac{1}{2}ay=\dfrac{1}{2}a\left(x-y\right)21ax−21ay=21a(x−y)知识点：因式分解章节：数学竞赛 / 数与式
