Question

(a*a+b*b-c*c+2ab)/(a*a-b*b+c*c+2ac)=?

Answer 1

((a^2 +b^2 +2 a b ) -c^2)/((a^2 +c^2 +2ac) -b^2)

⇒(a+b)^2 -c^2/((a+c)^2 -b^2
⇒ now we use 
one rule A^2 -B^2 =(A+B)*(A-B)

we get (a+b-c)/(a+c -c)