Simple....
you have: 

(The negative you have in front of this is either not supposed to be here or it's trying to trick you..)

Substitute the (-) into the equation-->>>

or

And then this turns into a very understandable math problem-->>
x*x= 

-5*x= -5x
-5*x= -5x
-5*-5= 25
Now we add it all up-->>>

-10x+25
Thus, your answer.