When solving the radical; SQRT1-2x = 1 + x

It says first step:

Square both sides:

=
1 – 2x = 1 + 2x + x^2

I am confused about where this part of the equation is coming from:
\/
1 – 2x = 1 + 2x + x^2

Question

When solving the radical; SQRT1-2x = 1 + x

It says first step:

Square both sides:

= 
1 – 2x = 1 + 2x + x^2

I am confused about where this part of the equation is coming from:
                      \/
1 – 2x = 1 + 2x + x^2

anonymous · Answer

(1 + x)^2
you're squaring both sides of the equation
foil it
you'll get 1 + 2x + x^2

anonymous · Answer

ohhhh wow u have to use FOIL alot in this lesson :P thx tho!!

anonymous · Answer

Yeah, learn to love foil =)

anonymous · Answer

yup 
have fun
foiling will get easier and faster the more you do it :D

anonymous · Answer

haha yes but it will never get less annoying!! ^^ lol

anonymous · Answer

Of course it will, then you'll move on to fun things like
(x^2 + 35x + 5)(3x^2 + 2x + 1)

anonymous · Answer

polpak