Question

complete the square.
x^2+2x=9
explain...

Answer 1

take half of 2, which is 1, and write
\[(x+1)^2=9+1^2=10\]

Answer 2

now that you have
\[(x+1)^2=10\] to solve take the square root and get
\[x+1=\pm\sqrt{10}\] so
\[x=-1\pm\sqrt{10}\]