help with algebraic factoring?

Unless you are familiar with complex numbers
then, =(7a-4i)(7a+4i)
whilst i^2=-1
God bless you.

If you can only factor it with real numbers, then you are right. However, you can factor it with complex numbers.

49a^2 + 16
= (7a)^2 - (-16)
= (7a)^2 - (i^2 * 4^2)
= (7a)^2 - (4i)^2
= (7a + 4i)(7a - 4i)

ya that can't be factored all you can do is isolate 49a^2=-16 then square both sides to get rid of the square and go from there