#### Description

The cancel command will cancel out any common factors appearing in the numerator and denominator of a fraction or several fractions. It will cancel out the greatest common divisor of the numerator and denominator.

To use the cancel command, simply go to the basic cancel page, type in your expression and hit the "Cancel" button. Your question will be automatically answered by computer and the reply will be shown in your browser within a few seconds. If you would like more control over how your question is answered, try the advanced cancel page, where there are a number of options which allow you to customize the command.

#### Examples

Here are some examples illustrating the types of expressions you can use the cancel command on and the results which QuickMath will return.

**Basic cancel command**

Expression | Result |

(1-x^2)/(1+x) | 1 - x |

(x^2+5x+6)/(x+2) | 3 + x |

(x^3+3x^2+3x+1)/(x+1) |
2 (1 + x) |

(1-4x+6x^2-4x^3+x^4)/(x^2-2x+1) |
2 1 - 2 x + x |

** Advanced cancel command**

Expression | Option | Result |

(sin(x)^2 cos(x)^2) / (sin(2x) cos(4x)) |
Trig |
2 cos(x) sec(4 x) sin(x) ----------------------- 2 |

(x^2+2x+1)/(x^2-1) + (x^2-4x)/(x^2-x) |
Modulo 3 |
1 + x 1 + ----- 2 + x |

(2-x^2)/(sqrt(2)-x) |
Automatic extensions |
sqrt(2) + x |

#### Options (advanced page only)

**Trig functions**

Values : checked or unchecked

Default : unchecked

When Trig functions is checked, the cancel command will treat trigonometric functions as rational functions of exponentials and manipulate them accordingly.

**Modulo**

Values : checked or unchecked + empty string or prime number or zero

Default : unchecked + empty string

When Modulo is checked and an integer n is entered into the modulo field, the calculations are carried out over the field of integers modulo n. When Modulo is unchecked or the text field contains 0 or is empty, the calculations are carried out over the field of integers.

**Field extensions**

Values : none or automatic or custom + custom extension expressions (only if the custom option is selected)

Default : none

Choosing the none option means that the calculations will be carried out over the field of integers (default).

Choosing the automatic option will extend the field over which the calculations are performed by any algebraic numbers appearing in the expression.

Choosing the custom option enables you to choose your own field extensions.