First we need to factor the left side. Since it is a perfect square (as is the process with completing the square, we know we can take half of the middle number along with x to be in the two parenthesis.
(x - 4)(x - 4) = 25
Now we simplify to show it as a square.
(x - 4)^2 = 25
Next we take the square root of both sides
x - 4 = +/- 5
Note that we have plus or minus 5. This is because either square would give us positive 25. Now we add 4 to both sides
x = 4 +/- 5
4 + 5 = 9
4 - 5 = -1
THE FIRST ONE AND THE LAST ONE
Okay, I worked it out and yes, it is a factor. Once you got x=-10, then you plug it into your formula. from there you can work it out like I did and get the answer. You can also input it into a scientific calcuator and figure it out that way. If you need any more help, go ahead and message me. Hope this helps. You can also but it into the box and divide it that way to find out. whichever way is better for you