# Straight line equations and inequalities

Thus the plane extends indefinitely in all directions. Step 2 Check one point that is obviously in a particular half-plane of that Straight line equations and inequalities to see if it is in the solution set of the inequality.

This means we must first multiply each side of one or both of the equations by a number or numbers that will lead to the elimination of one of the unknowns when the equations are added. Step 2 Adding the equations, we obtain Step 3 Solving for y yields Step 4 Using the first equation in the original system to find the value of the other unknown gives Step 5 Check to see that the ordered pair - 1,3 is a solution of the system.

We found that in all such cases the graph was some portion of the number line. Compare your solution with the one obtained in the example. Completing this unit should take you approximately 18 hours.

The resulting point is also on the line. Step 4 Find the value of the other unknown by substituting this value into one of the original equations. In this case there will be infinitely many common solutions. Determine the common solution of the two graphs. For example, if you want to determine the price for and amount of two types of candy for a party, you have the constraints of the total amount of candy needed GREATER than a given amount and the amount of money you can spend LESS than the amount you have.

Use the y-intercept and the slope to draw the graph, as shown in example 8.

Since the solution 2,-1 does check. Check this point x,y in both equations. In this case, solving by substitution is not the best method, but we will do it that way just to show it can be done.

Perpendicular means that two lines are at right angles to each other. First locate the point 0, Then solve the system. Which graph would be steeper: After carefully looking at the problem, we note that the easiest unknown to eliminate is y.

Instead of saying "the first term is positive," we sometimes say "the leading coefficient is positive.

Since we are dealing with equations that graph as straight lines, we can examine these possibilities by observing graphs. A graph is a pictorial representation of numbered facts.

If we add the equations as they are, we will not eliminate an unknown. Step 2 Add the equations. To eliminate x multiply each side of the first equation by 3 and each side of the second equation by We say "apparent" because we have not yet checked the ordered pair in both equations.

Example 2 Solve by addition: You can usually find examples of these graphs in the financial section of a newspaper. Compare the coefficients of x in these two equations. In this table we let y take on the values 2, 3, and 6. If the point chosen is not in the solution set, then the other half-plane is the solution set.

If an equation is in this form, m is the slope of the line and 0,b is the point at which the graph intercepts crosses the y-axis. Since the line itself is not a part of the solution, it is shown as a dashed line and the half-plane is shaded to show the solution set.

The zero point at which they are perpendicular is called the origin. Remember, there are infinitely many ordered pairs that would satisfy the equation. Otherwise, if the line is going down, it tells you that the distance is decreasing, which means that the train is approaching the station.

This scheme is called the Cartesian coordinate system for Descartes and is sometimes referred to as the rectangular coordinate system. Systems of Linear Equations and Inequalities You have seen in Units 2 and 5 that linear equations in one variable usually have 1 solution and linear equations in two variables have infinitely many solutions.

These skills are helpful when you are dealing with the motion of two or more objects: Then the graph is The slope of We now wish to compare the graphs of two equations to establish another concept.RWM Algebra / Unit 5: Graphs of Linear Equations and Inequalities Graphs of Linear Equations and Inequalities.

This unit is an introduction to graphing relationships between the two quantities on the coordinate plane. A graph helps visualize how one quantity depends on another. this graph would be a straight line. The slant of this. The equation of a straight line can be written in many other ways.

Another popular form is the Point-Slope Equation of a Straight Line. Footnote.

Country Note: Different Countries teach different "notation" (as sent to me by kind readers): In the. You can see the effect of different values of m and b at Explore the Straight Line Graph. Point-Slope Form. Another common one is the Point-Slope Form of the equation of a straight line: y − y 1 = m(x − x 1) Using Linear Equations.

You may like to read some of the things you can do with lines. Systems of Equations and Inequalities. In previous chapters we solved equations with one unknown or variable. We will now study methods of solving systems of equations consisting of two equations and two variables.

Graph a straight line using its slope and y-intercept. Straight Line Equations and Inequalities A: Linear Equations - Straight lines Please remember that when you are drawing graphs you should always label your axes and.

Equation of a Straight Line Equations of straight lines are in the form y = mx + c (m and c are numbers). m is the gradient of the line and c is the y-intercept (where the graph crosses the y-axis).

NB1: If you are given the equation of a straight-line and there is a number before the 'y', divide everything by this number to get y by itself, so.

Straight line equations and inequalities
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