Systems of Linear Equations

Systems of Linear Equations

Algebra 1

Mrs. LaGrange

In today's lesson you will learn how to answer the question, "Is (x,y) a solution to the system of equations?."

What is a system of linear equations?

*A system of linear equations is a set of two or more linear equations in the same variables.

*A system of linear equations must be solved at the same time, or simultaneously.

See the example to the right. This is an example of a system of linear equations.

Solutions of a system of linear equations:

*A solution to a system of linear equations in two variables is an ordered pair that is the solution of each equation.

In the case of our example when x = -1 and y = 2, both equations are true. The solution is (-1, 2).

Example:

Is (-1, 2) a solution to this example?

Let's find out:

1. Plug -1 in for x in both equations.
2. Plug 2 in for y in both equations.
3. Ask yourself, "Are both of the equations true?"
4. If the answer is yes, then this is a solution.

In the case of our example, (-1, 2) is a solution.

Multiple Choice

What are systems of linear equations?

• a set of two or more linear equations in the same variables
• a polynomial with three terms
• set of two or more linear inequalities in the same variables

Multiple Choice

• Yes

• No

Multiple Choice

• Yes

• No

Multiple Choice

• Yes

• No

Multiple Choice

• Yes

• No

A way of looking at things...

Another way to find out if a set of points, (x,y) is a solution is by looking at the graph.

A Graphical Approach

(One Solution)

Where ever the graphs of linear functions intersect we have a solution.

In this case we have one solution for the system y = -x + 7 and y = 2x + 1 at the point (2, 5).

A Graphical Approach

(No Solutions)

When lines never intersect, then there are no solutions to the system of equations.

Notice in the example that the lines have the same slope and different y-intercepts. (Recall: y=mx+b)

A Graphical Approach

(Infinitely Many Solutions)

Notice in the example that the equations look different at first, but after a little algebra, we see that they are the same line. There are infinitely many solutions.

Fill in the Blanks

Fill in the Blanks

Great work!

Your assignment for today is IXL Algebra U1 and U2. Strive for 85!

Helpful HInt: On section U2, remember how to use the slope intercept (y=mx+b) form to graph equations. Recall: m is the slope and b is the y-intercept. This will make things a lot easier.