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
The 4 on the left side is 10x more than the 4 on the right. This only works if the numbers are next to each other and are the same.
It's just one, if there isn't any other number attached to the x^2 you can just assume the leading coefficient is 1
Is this multiple chose? if so I would like to see the answers. But just using my brain, I would say, 5, or 7.