计算：1.（x-1)^2+2(1-x) 2.(x-y)/(x+3y)÷(x^2-y^2)/(x^2+6xy+9y^2)-2y/(x+y）

题目

计算：1.（x-1)^2+2(1-x) 2.(x-y)/(x+3y)÷(x^2-y^2)/(x^2+6xy+9y^2)-2y/(x+y）
1.（x-1)^2+2(1-x)
2.(x-y)/(x+3y)÷(x^2-y^2)/(x^2+6xy+9y^2)-2y/(x+y）

答案

1.（x-1)^2+2(1-x)
=(x-1)(x-1-2)
=(x-1)(x-3)
2.(x-y)/(x+3y)÷(x^2-y^2)/(x^2+6xy+9y^2)-2y/(x+y）
=(x-y)/(x+3y)×(x^2+6xy+9y^2)/(x^2-y^2)-2y/(x+y）
=(x-y)/(x+3y)×(x+3y)^2/[(x-y)(x+y)]-2y/(x+y）
=(x+3y)/(x+y)-2y/(x+y）
=(x+3y-2y)/(x+y)
=1