Answer:
(x -7)² = 100
Explanation:
You want to rewrite the equation x² -51 = 14x by completing the square.
Complete square
When we're finished, the equation will be of the form ...
(x +a)² = b
Expanding this, we have ...
x² +2ax +a² = b
That is, the value of 'a' is half the coefficient of x when the equation is written with the x-terms together.
Rearrangement
Adding 51 -14x to both sides of the given equation, we get ...
x² -51 = 14x
x² -14x = 51
Now, we can see that a=-14/2 = -7. We can add a² = (-7)² = 49 to both sides to complete the square:
x² -14x +49 = 51 +49
(x -7)² = 100 . . . . . . . rewritten equation