# Function simplify #

Simplify an expression tree.

Itâ€™s possible to pass a custom set of rules to the function as second argument. A rule can be specified as an object, string, or function:

```
var rules = [
{ l: 'n1*n3 + n2*n3', r: '(n1+n2)*n3' },
'n1*n3 + n2*n3 -> (n1+n2)*n3',
function (node) {
// ... return a new node or return the node unchanged
return node
}
]
```

The default list with rules is exposed on the function as `simplify.rules`

and can be used as a basis to built a set of custom rules.

For more details on the theory, see:

- Strategies for simplifying math expressions (Stackoverflow)
- Symbolic computation - Simplification (Wikipedia)

## Syntax #

```
simplify(expr)
simplify(expr, rules)
```

### Parameters #

Parameter | Type | Description |
---|---|---|

`expr` |
Node | string | The expression to be simplified |

`rules` |
Array<{l:string, r: string} | string | function> | Optional list with custom rules |

### Returns #

Type | Description |
---|---|

Node | Returns the simplified form of `expr` |

## Examples #

```
math.simplify('2 * 1 * x ^ (2 - 1)'); // Node {2 * x}
var f = math.parse('2 * 1 * x ^ (2 - 1)');
math.simplify(f); // Node {2 * x}
```