I accidentally just deleted some working and cannot get it back.
Can you help me with this please.
Factor fully: ( a² - b² - c² )² - 4b²c²
= (a²-b²-c²)² - (2bc)²
= (a² - b² - c² - 2bc)(a² - b² - c² + 2bc)
= (a² - (b + c)²)(a² - (b – c)²)