Factorisation

How would you factorise ab²-1+a-b² ?
As the whole equation doesn't have one common letter but if divided into two equations the -1 wouldn't fit if a or b was on the outside?

You can divide it into two equations a better way (assuming I get what you're saying)
As you have two positives and two negatives it makes sense to split them up to give
ab^2 + a - (b^2 + 1)
Can you see how to factorise this?

Thank you!
So would it be
ab²+a-(b²+1)
a(b²+1) - (b²+1)
so a(b²+1)