Ok so when you complete the square with a binomial that looks like
[tex]x^{2}+bx[/tex]
you add
[tex](\frac{b}{2})^{2}[/tex]
So that it factors into
[tex](x+\frac{b}{2})^{2}[/tex]
So, 2/2 squared is 1, so add it to both sides and we get
[tex]x^{2}+2x+1=10[/tex]
Then the right side factors and it becomes
[tex](x+1)^{2}=10[/tex]
