I think its a :) if not c
Answer:
10x-20
Step-by-step explanation:
5(2x-4)
5x2=10
5x4=20
For any equation,

assume solution of a form, 
Which leads to,

Simplify to,

Then find solutions,

For non repeated real root y, we have a form of,

Following up,
For two non repeated complex roots
where,

and,
the general solution has a form of,

Or in this case,

Now we just refine and get,

Hope this helps.
r3t40