How to make brackets bigger?

Question

I have the following expression here.

$$\{\|\frac{f_i(x_i+h)-f_i(x-k)}{h}\|\}$$

I want to make the outer most brackets and the modulus sign to be bigger.

I have tried

$$\Bigg{\Bigg|\frac{f_i(x_i+h)-f_i(x-k)}{h}\Bigg|\Bigg}$$

but this doe not seem to work.

What can I do?

Answer 1

\Bigg{ and \Bigg} are errors; it should be \Bigg\{ and \Bigg\}, respectively.

Actually, there's no need to \Bigg (pun intended) -- \bigg is the correct size for the fractional term at hand. Thus, you should enter the displayed equation as follows:

\[
\biggl\{\biggl| \frac{f_i(x_i+h)-f_i(x-k)}{h} \biggr|\biggr\}
\]

Note that I use \biggl and \biggr instead of just \bigg for the "fence symbols". For the present equation this makes no difference in appearance. However, there would be a major difference if the fractional expression were preceded by a unary minus (or plus) symbol.

Answer 2

You can try \right\{ and \left\{. These commands adjust the size of the braces to their contents.