You can enter mathematical expressions in your comments.
To enter a mathematical expression:

In the Show My Work toolbar, click Insert Math.
The toolbar changes to display buttons for entering math expressions.

Use the keyboard and buttons to enter your math expression.
To do this  Do this 

Enter variables.  Type the variable name. Variables are automatically
italicized. 
Enter lowercase or uppercase Greek letters.  Type a backslash (\) followed by the lowercase or capitalized
name of the letter, for example, \delta to
insert δ or
\Delta to insert Δ. 
Display or hide additional buttons.  Click Functions,
Symbols,
Operators, Calculus,
Vectors, or
Greek. 
Move the insertion point.  Press the home,
END, and arrow
keys. 
Move to the next part of the expression.  Press TAB. 
Move to the previous part of the expression.  Press SHIFT+TAB. 
Copy the entire expression.  Press CTRL+C. Note: You cannot select or copy only part of
the expression.

Cut the entire expression.  Press CTRL+X. Note: This removes the entire expression. To
undo, press CTRL+V
to paste the expression.

Paste the entire expression.  Press CTRL+V. Important: This replaces the
entire expression with an expression that you previously cut or
copied. There is no undo.

Delete the character to the left of the insertion point, the
selected expression, or notation such as fractions.  Press BACKSPACE. 
Delete the character to the right of the insertion point, the
selected expression, or notation such as fractions.  Press DELETE. 
Delete the current part of the expression and its parent — for
example, deletes an entire fraction.  Press CTRL+DELETE. 
Note:
 You cannot select a portion of your math expression to cut, copy, or
paste.
 You cannot undo changes in your math expression.
Examples: Entering Math Notation
The following examples illustrate entry of some common expressions.
Expression  Do this  To display this 

A simple expression with integers  Type 2x+52500 
$2x+52500$

A polynomial with a fractional coefficient 
 Click
 Type 1 and press TAB
 Type 2 and press TAB
 Type x^2 and press TAB
 Type +4x+2

$\frac{1}{2}{x}^{2}+4x+2$

A simple inequality 
 Type x
 Click
 Type 4

$x\ge 4$

A square root  Type sqrt(x 
$\sqrt{x}$

A cube root 
 Click
 Type 3TABx

$\sqrt[3]{x}$

An expression involving pi and Euler's number  Type \pi+e^2 
$\pi +{\mathit{e}}^{2}$

The natural logarithm of an absolute value 
 Click
 Type x

$\mathrm{ln}\left(\leftx\right\right)$

A complex number  Type 2+3i 
$2+3\mathit{i}$

A vector in vector bracket form 
 Click
 Type 12,15,22

$\u27e812,15,22\u27e9$
