题目计算：(1)(1a+1+ a2−2a+1a2−1)÷a−1a+1\text{(}1\text{)}(\dfrac{1}{a+1}+\dfrac{\text{ }a^{2}-2a+1}{a^{2}-1})\text{÷}\dfrac{a-1}{a+1}(1)(a+11+a2−1 a2−2a+1)÷a+1a−1； (2)x2−y2x2+2xy+y2÷(x2−xyx+y).\ \ (2)\dfrac{x^{2}-y^{2}}{x^{2}+2xy+y^{2}}\text{÷}(\dfrac{x}{2}-\dfrac{\text{xy}}{x+y}). (2)x2+2xy+y2x2−y2÷(2x−x+yxy).知识点：平方差公式、完全平方公式、分式的混合运算章节：第11章 整式的乘除 / 11.2 乘法公式
