Difference Between Linear Equations & Linear Inequalities

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Algebra is the division of math concerned with operations and relations. Its areas of focus range from solving equations and inequalities to graphing functions and polynomials. Algebra’s complexity grows with increasing variables and operations, but it starts its foundation in linear equations and inequalities.

TL;DR (Too Long; Didn't Read)

Key differences between linear equations and inequalities include the number of possible solutions and how they're graphed.

Linear Equations

A linear equation is any equation involving one or two variables whose exponents are one. In the case of one variable, one solution exists for the equation. For example, with

2x = 6

x​ can only be 3.

Linear Inequalities

A linear inequality is any statement involving one or two variables whose exponents are one, where inequality rather than equality is the center of focus. For instance, with

3y < 2

the “<” represents less than and the solution set includes all numbers

y < 2/3

Equation Solutions

One obvious difference between linear equations and inequalities is the solution set. A linear equation of two variables can have more than one solution.

For instance, with

x = 2y + 3

(5, 1), then (3, 0) and (1, -1) are all solutions to the equation.

In each pair, ​x​ is the first value and ​y​ is the second value. However, these solutions fall on the exact line described by

y = \frac{1}{2} x - \frac{3}{2}

Inequality Solutions

If the inequality were

x > 2y + 3

multiple solutions would exist, for example (3, -1), (3, -2), (3, -3) and many others, where more than one solution can exist for the same value of ​x​ or the same value of ​y​ only for inequalities. The first number in each pair is the ​x​ value and the second is the ​y​ value.

Graph Lines

The graph of linear inequalities include a dashed line if they are greater than or less than but not equal to. Linear equations, on the other hand, include a solid line in every situation. Moreover, linear inequalities include shaded regions whereas linear equations do not.

Equation Complexities

The complexity of linear inequalities outweighs the complexity of linear equations. While the latter involves simple slope and intercept analysis, the former (linear inequalities) also involves deciding where to shade in the graph as you account for the additional set of solutions.


About the Author

Sky Smith has been writing on psychology, electronics, health and fitness since 2002 for various online publications. He graduated from the University of Florida with honors in 2005, earning a Bachelor of Science in psychology and statistics with a minor in math.