Need help with this Roots and Remainders question!

How to find numerical difference of equation with complex roots (roots that aren't integers)?

What do you mean by 'numerical difference of equation' ?

I really don't know but as far I can understand, they're talking about the difference between the roots of the given quadratic equation.
Here's the question:
The numerical difference between the roots of x^2 -7x-9=0 is:-
i)85^½
ii)9(7^½)
iii)2(85^½)
iv)5
I don't have underroot sign in my keyboard. Sorry if it's confusing you.

You know a formula for the the two roots of a quadratic equation. Subtract one from the other and what do you get? Now plug in the numbers.

I don't get it. Are you talking about the quadratic formula?

Yes.