(x的-1次方+y的-1次方)÷(x的-2次方-y的-2次方)
=(1/x+1/y)÷(1/x+1/y)(1/x-1/y)
=1/(1/x-1/y)
=xy/(y-x);解方程x-4分之4=4-x分之1+3会解吗