# How Do You Solve a Matrix in Game Theory?

//

Diego Sanchez

Game theory is an important concept in mathematics and economics, which deals with the study of decision-making in situations where multiple players are involved. One of the key tools used in game theory is the matrix, which helps in representing the different strategies available to each player and their corresponding outcomes. In this article, we will explore how to solve a matrix in game theory.

## What is a Matrix?

A matrix is a rectangular array of numbers or variables, arranged in rows and columns. In game theory, matrices are used to represent the strategies available to each player and their corresponding payoffs. The rows of the matrix represent the different strategies available to one player, while the columns represent the strategies available to the other player.

### Types of Matrices

There are two main types of matrices used in game theory: normal-form games and extensive-form games. Normal-form games are represented by a simple matrix, where each row represents a strategy for one player and each column represents a strategy for another player. Extensive-form games are represented by a tree-like diagram that shows all possible moves and outcomes.

### Solving a Matrix

To solve a matrix in game theory, we need to find the Nash equilibrium, which is a set of strategies where no player has an incentive to change their strategy unilaterally. In other words, it’s a point where both players have reached an optimal outcome.

One way to find the Nash equilibrium is by using dominant strategy elimination. A dominant strategy is one that always yields better results than any other strategy regardless of what other players do. By eliminating dominated strategies (those that are always worse than another strategy), we can simplify the matrix until we reach only one or few remaining options.

Another method is called mixed-strategy Nash equilibrium, which involves assigning probabilities to each possible move rather than selecting one single move. This allows players to randomly select a strategy based on the probability assigned to each move. A mixed-strategy Nash equilibrium is reached when no player can improve their expected payoff by unilaterally changing their strategy.

### Example

Let’s consider a simple example of a game between two players, player A and player B. Each player has two possible strategies: cooperate or defect. The payoffs for each player are represented in the matrix below:

• If both players cooperate, they each receive a payoff of 3.
• If one player cooperates and the other defects, the defector receives a payoff of 5 while the cooperator receives only 1.
• If both players defect, they each receive a payoff of 2.
Cooperate Defect
Cooperate (3,3) (1,5)
Defect (5,1) (2,2)

By using dominant strategy elimination, we can eliminate the dominated strategy of cooperation for both players. Therefore, the only remaining option is for both players to defect (D,D), which is the Nash equilibrium.

In conclusion, matrices are an essential tool in game theory for representing different strategies and outcomes. By solving these matrices using dominant strategy elimination or mixed-strategy Nash equilibrium methods, we can identify the optimal strategies for each player and reach a Nash equilibrium.