The polynomial would be 2x+5.
We bring down the first number inside the box, 2, unchanged.
_______
-1| 2 7 5
_______
2
Now we multiply that 2 by the number outside, -1:
_______
-1| 2 7 5
-2
2
Now we add the two numbers in the middle column:
________
-1| 2 7 5
-2
2 5
Multiply the 5 we brought down by the -1:
________
-1| 2 7 5
-2 -5
2 5
Add the numbers in the last column:
________
-1| 2 7 5
-2 -5
2 5 0
The 3 numbers under the box represent the coefficients of x² and x, as well as the constant. When we finish, we no longer have an x², but start at the next level down, which would be x. 2 would be the coefficient of x and 5 would be the constant, with 0 remainder.