(b-a)^2 / (a^2-b^2)=

(d^2-c^2) / (c-d)^2=

(b-a)^2 / (a^2-b^2)=-(a-b)²/(a-b)(a+b)=-(a-b)/(a+b)=(b-a)/(a+b)(d^2-c^2) / (c-d)^2=(d-c)(d+c)/-(d-c)²=(d+c)/-(d-c)=(d+c)/(-d+c)