1)
c²- x²- 2xy - y² =
= c²- (x²+ 2xy + y²) =
= c²- (x+у)² =
= (с-х-у)·(с+х+у)
2)
a⁶ - a⁴ + a² - 1 =
= (a⁶ - a⁴) + (a² - 1) =
= а⁴ · (a² - 1) + (a² - 1) =
= (a² - 1)·(a⁴ + 1) =
= (а-1)·(а+1)·(а⁴+1)
