This code:

```
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows,shapes,positioning}
\usetikzlibrary{calc,decorations.markings}
\tikzstyle{block} = [rectangle, draw, fill=blue!10, rounded corners, text centered, text width = 7em, minimum height = 2em]
\tikzstyle{line} = [draw, -latex']
\begin{document}
\begin{tikzpicture}[]
% Place nodes
\node [block] (optimization) {Given \\optimization problem};
\node [block, right of=optimization, node distance=4cm] (critical) {Find \\ critical points};
\node [block, right of = critical, node distance=4cm] (second) {Apply Second Derivatives Test to each critical point};
\node[block, below left=1cm and 1cm of second](case one) {$D(a, b) = 0$};
\node[block, below = 1cm of second](case two) {$D(a, b) >0$};
\node[block, below right = 1cm and 1cm of second](case three) {$D(a, b) < 0$};
\node[block, below = 1cm of case one](no info){No information about critical point $(a, b)$};
\node[block, below = 1cm of case two](saddle){$(a, b)$ is a saddle point};
\node[block, below = 1cm of case three](more){Check $f_{xx}(a, b)$};
\node[block, below left = 1cm and 0.1cm of more](a){$f_{xx}(a, b) > 0$};
\node[block, below right = 1cm and 0.1cm of more](b){$f_{xx}(a, b) < 0$};
\node[block, below = 1cm of a](min){$(a, b)$ is a local min};
\node[block, below = 1cm of b](max){$(a, b)$ is a local max};
% Draw edges
\path [line] (optimization) -- (critical);
\path [line] (critical) -- (second);
\path [line](second) -- (case one);
\path [line] (second) -- (case two);
\path [line] (second) -- (case three);
\path[line] (case one) -- (no info);
\path[line] (case two) -- (saddle);
\path[line] (case three) -- (more);
\path[line] (more) -- (a);
\path[line] (more) -- (b);
\path[line] (a) -- (min);
\path[line] (b) -- (max);
\end{tikzpicture}
\end{document}
```

has produce the flow chart:

I am pretty happy with everything, except I would like the two nodes under "Check f_{xx}(a, b)" to be closer together. I thought I should be able to do this by doing something like:

`\node[block, below left = 1cm and 0.1cm of more](a){$f_{xx}(a, b) > 0$}`

and

`\node[block, below right = 1cm and 0.1cm of more](b){$f_{xx}(a, b) < 0$}`

but this did not work. Any suggestions?

## Best Answer

You can be a little bit sneaky and use a negative value for the x-direction. Below I used

`below right = 1cm and -1cm of more`

. I also changed to`\tikzset`

instead of`\tikzstyle`

as the former is recommended, added the`block`

style to all nodes, and used a loop to draw the arrows.## Second alternative

Another option would be to use the

`on grid`

option for those two nodes. With`on grid`

, the node distance is calculated from the center of the nodes, instead of the border. Note that you need the place`on grid`

before the`below ...`

, i.e.Complete code: