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📈college algebra review

Linear Interpolation

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Linear interpolation is a method used to estimate the value of a function between two known data points by assuming a linear relationship between them. It involves finding the equation of the line that passes through the two points and using it to calculate the unknown value.

5 Must Know Facts For Your Next Test

  1. Linear interpolation is a simple and widely used method for estimating unknown values within a known range of data.
  2. The accuracy of linear interpolation depends on the linearity of the function and the proximity of the unknown point to the known data points.
  3. Linear interpolation is often used in various fields, such as engineering, science, and finance, to estimate missing data or to perform calculations based on available information.
  4. The formula for linear interpolation is: $y = y_1 + \frac{(y_2 - y_1)}{(x_2 - x_1)}(x - x_1)$, where $(x_1, y_1)$ and $(x_2, y_2)$ are the known data points.
  5. Linear interpolation assumes that the function is linear between the known data points, which may not always be the case for more complex functions.

Review Questions

  • Explain the purpose and application of linear interpolation in the context of linear functions.
    • The purpose of linear interpolation in the context of linear functions is to estimate the value of a function at a point within the range of known data points, assuming a linear relationship between them. This is useful when you have two known data points on a linear function and need to find the value of the function at an intermediate point. For example, if you know the prices of a product at $x_1 = 5$ units and $x_2 = 10$ units, you can use linear interpolation to estimate the price at $x = 7$ units, assuming a linear relationship between the price and the number of units.
  • Describe the limitations of using linear interpolation and how it differs from extrapolation.
    • The main limitation of linear interpolation is that it assumes a linear relationship between the known data points, which may not always be the case for more complex functions. Linear interpolation is only valid within the range of the known data points, and it becomes less accurate as the unknown point moves further away from the known points. In contrast, extrapolation involves estimating the value of a function outside the range of the known data points, which can be much less reliable, as the function may not maintain the same linear relationship beyond the known range. While linear interpolation is a simple and widely used method, it is important to consider the limitations and the underlying assumptions when applying it to estimate unknown values.
  • Analyze how the accuracy of linear interpolation is affected by the proximity of the unknown point to the known data points and the linearity of the function.
    • The accuracy of linear interpolation is highly dependent on two key factors: the proximity of the unknown point to the known data points and the linearity of the function. When the unknown point is closer to the known data points, the linear interpolation is more likely to provide a reliable estimate, as the assumption of a linear relationship between the points is more valid. However, as the unknown point moves further away from the known data points, the linear interpolation becomes less accurate, as the function may not maintain a linear behavior over a larger range. Additionally, the linearity of the function itself is crucial. If the function is truly linear, linear interpolation will provide a very accurate estimate. But if the function is non-linear, the accuracy of the linear interpolation will decrease, and it may not be the most appropriate method to use. Understanding these factors is essential when applying linear interpolation to estimate unknown values in the context of linear functions.

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