（xy分之X的平方-Y的平方）的平方除以【（X+Y）*（X分之X-Y）的3次方]除以y的平方分之x
=[（x^2-y^2)^2/x^2y^2]÷[x^2-y^2)(x-y)^2/x]^3÷（x/y^2)
=[（x^2-y^2)^2/x^2y^2]*[x^3/(x^2-y^2)(x-y)^2]*y^2/x
=(x^2-y^2)/(x-y)^2
=(x+y)/(x-y)
=(x/y+1)/(x/y-1)
=(-2/3+1)/(-2/3-1)
=-1/5