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Mathematics LibreTexts

Key Terms Chapter 04: Graphs

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Boundary Line
The line with equation Ax+By=C that separates the region where Ax+By>C from the region where Ax+By<C.
Geoboard
A geoboard is a board with a grid of pegs on it.
Graph of a Linear Equation
The graph of a linear equation Ax+By=C is a straight line. Every point on the line is a solution of the equation. Every solution of this equation is a point on this line.
Horizontal Line
A horizontal line is the graph of an equation of the form y=b. The line passes through the y-axis at (0,b).
Intercepts of a Line
The points where a line crosses the x-axis and the y-axis are called the intercepts of the line.
Linear Equation
A linear equation is of the form Ax+By=C, where A and B are not both zero, is called a linear equation in two variables.
Linear Inequality
An inequality that can be written in one of the following forms:

Ax+By>CAx+ByCAx+By<CAx+ByC

where A and B are not both zero.
Negative Slope
A negative slope of a line goes down as you read from left to right.
Ordered Pair
An ordered pair (x,y) gives the coordinates of a point in a rectangular coordinate system.
Origin
The point (0,0) is called the origin. It is the point where the x-axis and y-axis intersect.
Parallel Lines
Lines in the same plane that do not intersect.
Perpendicular Lines
Lines in the same plane that form a right angle.
Point–Slope Form
The point–slope form of an equation of a line with slope m and containing the point (x1,y1) is yy1=m(xx1).
Positive Slope
A positive slope of a line goes up as you read from left to right.
Quadrant
The x-axis and the y-axis divide a plane into four regions, called quadrants.
Rectangular Coordinate System
A grid system is used in algebra to show a relationship between two variables; also called the xy-plane or the ‘coordinate plane’.
Rise
The rise of a line is its vertical change.
Run
The run of a line is its horizontal change.
Slope Formula
The slope of the line between two points (x1,y1) and (x2,y2) is m=y2y1x2x1.
Slope of a Line
The slope of a line is m=riserun. The rise measures the vertical change and the run measures the horizontal change.
Slope-Intercept Form of an Equation of a Line
The slope–intercept form of an equation of a line with slope m and y-intercept, /((0,b)\) is, y=mx+b.
Solution of a Linear Inequality
An ordered pair (x,y) is a solution to a linear inequality the inequality is true when we substitute the values of x and y.
Vertical Line
A vertical line is the graph of an equation of the form x=a. The line passes through the x-axis at (a,0).
X-intercept
The point (a,0) where the line crosses the x-axis; the x-intercept occurs when y is zero.
X-coordinate
The first number in an ordered pair (x,y).
Y-coordinate
The second number in an ordered pair (x,y).
​​​​​​​Y-intercept
The point (0,b) where the line crosses the y-axis; the y-intercept occurs when x is zero.

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