Answer 1

(y^2-1)(y^2+1)

Answer 2

as (a^2 -B^2)=(a-b)(a+b)

Answer 3

y^4-1 = (y^2-1)(y^2+1) = (y-1)(y+1)(y^2+1)

Answer 4

Thanks

Answer 5

can anyone explain please?

Answer 6

i did so???

Answer 7

y^4-1 = (y^2)^2 - 1^2
use the formula
a^2 -B^2=(a-b)(a+b)
so you get
(y^2-1)(y^2+1)
then use the formula again for (y^2-1)
so the final answer would be

(y-1)(y+1)(y^2+1)