# Formula Manipulation and Simplification

Simplify or modify expressions, substitute parts of expressions

Transform your expression into the particular form you require (expanded, factored, or expressed in particular terms) by choosing the appropriate function. See Choose Function to Rearrange Expression. If you just need a simpler expression, use `simplify`. You also can substitute for any part of an expression with another value by using `subs`.

 Simplify Symbolic Expression Simplify symbolic expressions in Live Editor

## Functions

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 `simplify` Algebraic simplification `simplifyFraction` Simplify symbolic rational expressions `subexpr` Rewrite symbolic expression in terms of common subexpressions

#### Polynomials & Fractions

 `coeffs` Coefficients of polynomial `expand` Expand expressions and simplify inputs of functions by using identities `horner` Horner nested polynomial representation `numden` Extract numerator and denominator `partfrac` Partial fraction decomposition

#### Rewriting & Decomposition

 `children` Subexpressions or terms of symbolic expression `collect` Collect coefficients `combine` Combine terms of identical algebraic structure `compose` Functional composition `displayFormula` Display symbolic formula from string `divisors` Divisors of integer or expression `factor` Factorization `isolate` Isolate variable or expression in equation `lhs` Left side (LHS) of equation `mapSymType` Apply function to symbolic subobjects of specific type `rewrite` Rewrite expression in terms of another function `rhs` Right side (RHS) of equation
 `subexpr` Rewrite symbolic expression in terms of common subexpressions `subs` Symbolic substitution

## Topics

Choose Function to Rearrange Expression

Several functions are available to manipulate expressions. Understand which function to use.

Simplify Symbolic Expressions

Simplifying symbolic expressions, including assumptions and additional options.

Substitute Variables in Symbolic Expressions

Substitute variables with other variables, numbers, vectors, or matrices.

Evaluate Symbolic Expressions Using subs

Evaluate expressions and functions after their variables are assigned values.

Developing an Algorithm for Undistorting an Image

This example develops a mathematical model using the Symbolic Math Toolbox to undistort an image and features a local function in the live script.

Abbreviate Common Terms in Long Expressions

Simplify the display of long expressions by abbreviating common terms.

## Support

#### Mathematical Modeling with Symbolic Math Toolbox

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