Question

初二数学 化简求值

要写详细过程

Answer 1

解
原式
=[x(x-y)+y(x+y)-2xy]/(x²-y²)
=[x²-xy+xy+y²-2xy]/(x+y)(x-y)
=(x²-2xy+y²)/(x+y)(x-y)
=(x-y)²/(x+y)(x-y)
=(x-y)/(x+y)
=(5-2)/(5+2)
=3/7

Answer 2

原式=[x(x-y)+y(x+y)]/(x^2-y^2)-2xy/(x^2-y^2)
=(x^2-xy+xy+y^2)/(x^2-y^2)-2xy/(x^2-y^2)
=(x^2+y^2-2xy)/(x^2-y^2)
=(x-y)^2/(x+y)*(x-y)
=(x-y)/(x+y)
=(5-2)/(5+2)
=3/7