# Matrix and equations

The rule for matrix multiplicationhowever, is that two matrices can be multiplied only when the number of columns in the first equals the number of rows in the second i. Any matrix can be multiplied element-wise by a scalar from its associated field. For example, the rotation of vectors in three- dimensional space is a linear transformation, which can be represented by a rotation matrix R: ## A Matrix Multi-Tool for the HP 35s Programmable Calculator

A solution of a linear system is an assignment of values to the variables x1, x2, The set of all possible solutions is called the solution set. A linear system may behave in any one of three possible ways: The system has infinitely many solutions.

The system has a single unique solution. The system has no solution. Geometric interpretation[ edit ] For a system involving two variables x and yeach linear equation determines a line on the xy- plane.

Because a solution to a linear system must satisfy all of the equations, the solution set is the intersection of these lines, and is hence either a line, a single point, or the empty set. For three variables, each linear equation determines a plane in three-dimensional spaceand the solution set Matrix and equations the intersection of these planes.

Thus the solution set may be a plane, a line, a single point, or the empty set. For example, as three parallel planes do not have a common point, the solution set of their equations is empty; the solution set of the equations of three planes intersecting at a point is single point; if three planes pass through two points, their equations have at least two common solutions; in fact the solution set is infinite and consists in all the line passing through these points.

The solution set is the intersection of these hyperplanes, and is a flatwhich may have any dimension lower than n. General behavior[ edit ] The solution set for two equations in three variables is, in general, a line.

In general, the behavior of a linear system is determined by the relationship between the number of equations and the number of unknowns. Here, "in general" means that a different behavior may occur for specific values of the coefficients of the equations.

In general, a system with fewer equations than unknowns has infinitely many solutions, but it may have no solution. Such a system is known as an underdetermined system. In general, a system with the same number of equations and unknowns has a single unique solution. In general, a system with more equations than unknowns has no solution.

Such a system is also known as an overdetermined system. The following pictures illustrate this trichotomy in the case of two variables: One equation Two equations Three equations The first system has infinitely many solutions, namely all of the points on the blue line.

The second system has a single unique solution, namely the intersection of the two lines. The third system has no solutions, since the three lines share no common point. It must be kept in mind that the pictures above show only the most common case the general case.

It is possible for a system of two equations and two unknowns to have no solution if the two lines are parallelor for a system of three equations and two unknowns to be solvable if the three lines intersect at a single point.

A system of linear equations behave differently from the general case if the equations are linearly dependentor if it is inconsistent and has no more equations than unknowns. Independence[ edit ] The equations of a linear system are independent if none of the equations can be derived algebraically from the others.

When the equations are independent, each equation contains new information about the variables, and removing any of the equations increases the size of the solution set. For linear equations, logical independence is the same as linear independence. For example, the equations.Hi there! This page is only going to make sense when you know a little about Systems of Linear Equations and Matrices, so please go and learn about those if you don't know them already!

Using Matrices makes life easier because we can use a computer program (such as the Matrix Calculator) to . Definition. A matrix is a rectangular array of numbers or other mathematical objects for which operations such as addition and multiplication are defined.

Most commonly, a matrix over a field F is a rectangular array of scalars each of which is a member of F.