Answer:
1
Step-by-step explanation:
By adding 1 on both sides we get:
[tex]x^2+2x+1 = -1+1 = 0[/tex]
By adding such we get on the left a perfect square trinomial (a trinomial that is the result of squaring a binomial):
[tex]x^2 +2x+1 = (x+1)^2[/tex]
To decide what to add, understand what is the result of squaring a binomial of the form: [tex](x+c)\\(x+c)^2 = (x+c)(x+c) = x^2 +2*c*x + c^2[/tex]
In your case, 2*c*x is "2x" therefore the value of c must be 1.
so to complete the square you need to add [tex]c^2[/tex] which will result in [tex]1^2= 1[/tex]
