$$\\(2x+1)^2=16\quad|\quad\sqrt{}\\
2x+1=4\quad|\quad-1\\
2x=3\quad|\quad:2\\
x=\frac{3}{2} \quad or \quad x=1.5$$
Don't forget the other solution!
If (2x+1)2 = 16 then 2x+1 = ±4
Taking the negative value we have 2x+1 = -4; 2x = -5; x = -5/2 or x = -2.5
I think that you have forgotten one of the answers heureka.
$$(2x+1)^2=16\\
2x+1=4\quad or \quad 2x+1=-4\\
2x=3\quad \:\:\:\:or \quad 2x=-5\\$$
$$x=1\frac{1}{2}\quad or \quad x=-2\frac{1}{2}\\$$
I was your looking at your LaTex code heureka, I've not seen the \quad command before.
I used it in my answer. Thank you.