A math extrapolate formula is an equation used to predict the value of the dependent variable from an independent variable not found within the range of data. An example of such a formula is y=2x+5, when the range of values for x is normally between 0 and 10. If the value of x is 20, it can still be plugged into the equation to find that y=2(20)+5=45.

A math extrapolate formula is an example of extrapolation. Extrapolation is the process of predicting a value based on what is already known. Making predictions based on what has already been given can be done through either extrapolation or interpolation. Interpolation involves predicting the value of the dependent variable based on the value of the independent variable that is within a known data range.

When working with statistics and data, interpolation is usually the preferred method because it increases the likelihood that the estimation is valid. Two factors are considered when working with either extrapolation or interpolation, the least square line or best fit and the function. The first describes a curve or line that approximates that data. The latter establishes a relationship between the independent variable and the dependent variable. Extrapolation is used in mathematics and science and can have applications in fields such as history.