a2-an-8a*8b

Assuming the expression is a^2 - a n - 8a*8b (with * as multiplication and an meaning a·n):

• 8a*8b = 64ab
• The expression becomes a^2 - a n - 64 a b
• Factor out a: a (a - n - 64 b)

So the factored form is: a (a - n - 64 b)

If you meant a^2 - a^n - 8a*8b (i.e., a^n instead of a n), let me know — the factoring would be different.