It is given in the question that
[tex](x+1)^2 = 55[/tex]
Now we need to get rid of square, and for that we take square root to both sides, that is
[tex]\sqrt {(x+1)^2} = \pm \sqrt{55}[/tex]
[tex]x+1 = -\sqrt{55} , x+1 = \sqrt{55}[/tex]
Subtracting 1 in both equations
[tex]x = - \sqrt{55}-1 , x = \sqrt{55}-1 \\ x = -8.42 , 6.42[/tex]
Therefore , out of the given option, correct option is the third option
