# Function simplify Simplify an expression tree. It'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)](http://stackoverflow.com/questions/7540227/strategies-for-simplifying-math-expressions) - [Symbolic computation - Simplification (Wikipedia)](https://en.wikipedia.org/wiki/Symbolic_computation#Simplification) ## Syntax ```js 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 ```js 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} ``` ## See also [derivative](derivative.md), [parse](parse.md), [eval](eval.md)