Chapter 8 - Section 8.1 - The Square Root Property and Completing the Square - Exercise Set - Page 595: 103

Makes sense. In order to complete the square, you need to get the square of half the value of the coefficient of the x-term, which is $(\frac{10}{2})^2$. Thus, you need to add $25$ on both sides to complete the square.

Makes sense. In order to complete the square, you need to get the square of half the value of the coefficient of the x-term, which is $(\frac{10}{2})^2$. Thus, you need to add $25$ on both sides to complete the square.