Question 140162
your solution:
a^4+b^4-c^4+2a^2b^2
(a^4-2a^2b^2+b^4)-c^4
(a^2-b^2)^2-(c^2)^2
(a^2-b^2-c^2)(a^2-b^2+c^2) as my answer

my solution
a^4+b^4-c^4+2a^2b^2
(a^4+2a^2b^2+b^4)-c^4 (is +2a^2b^2)
then
(a^2+b^2)^2-(c^2)^2
(a^2+b^2-c^2)(a^2+b^2+c^2)