Help I don’t understand the first part but understand the second

Answer:
Step-by-step explanation:
Complete the square
[tex]x^{2}[/tex] + 2x - 13 = 0
[tex]x^{2}[/tex] + 2x = 13
[tex]x^{2}[/tex] + 2x + [tex]1^{2}[/tex] = 13 +1 (take 1/2 of the b term , the 2 )
[tex]x^{2}[/tex] + 2x + 1 = 14
(x +1)^2 = 14
Answer:
Complete the square: