题目下列因式分解正确的一项是（ ）A.x2+y2=(x+y)2x^{2}+y^{2}=\left(x+y\right)^{2}x2+y2=(x+y)2B.x2−4=(x+2)(x−2)x^{2}-4=\left(x+2\right)\left(x-2\right)x2−4=(x+2)(x−2)C.x2−2x−1=(x−1)2x^{2}-2x-1=\left(x-1\right)^{2}x2−2x−1=(x−1)2D.2xy+4x=2(xy+2x)2xy+4x=2\left(xy+2x\right)2xy+4x=2(xy+2x)知识点：提公因式法章节：数与式 / 因式分解
