Problem 73 - Algebra 2

Question

Find the slope of each line. $$ y=\frac{-x}{9} $$

Step-by-Step Solution

Answer

\( m = \frac{-1}{9} \)

Step 1: Write in slope-intercept form

The equation \(y = \frac{-x}{9} = -\frac{1}{9}x\) is already in slope-intercept form \(y = mx + b\) with \(b = 0\).

Step 2: Identify the slope

The slope is \(m = -\frac{1}{9}\).

Key Concepts

Slope-Intercept Form

Understanding the slope-intercept form of a linear equation is foundational for grasping the concept of the slope of a line. In its simplest form, the slope-intercept form is expressed as \( y = mx + b \), where

• \( m \) represents the slope of the line,
• \( x \) and \( y \) are the variables representing coordinates on a graph, and
• \( b \) is the y-intercept, which is the point where the line crosses the y-axis.

If a line is placed on a coordinate graph, the slope \( m \) determines how steep the line is. A positive slope means that the line goes up from left to right, whereas a negative slope means that the line goes down as it moves from left to right. If the slope is zero, the line is horizontal, meaning it doesn't rise or fall at all. To find the slope of a line from an equation in slope-intercept form, you simply look for the coefficient of \( x \) as it will directly give you the slope of the line. In our example problem, \( y = \frac{-x}{9} \), the equation is already in slope-intercept form, and the coefficient of \( x \) is \( \frac{-1}{9} \), which means the slope of the line is \( \frac{-1}{9} \).

Linear Equations

Linear equations are the simplest type of equations in algebra and have wide applications in many fields. They form straight lines when graphed on a coordinate plane. The standard form of a linear equation is \( Ax + By = C \), where

• \( A \), \( B \), and \( C \) are constants, and
• \( x \) and \( y \) are variables that represent any point on the line.

A key characteristic of linear equations is that they have one degree, which means that both variables are to the first power (no squared terms or higher powers). When a linear equation is manipulated into the slope-intercept form \( y = mx + b \), it becomes much easier to graph and understand the slope of the line, as it visually and algebraically represents how the line behaves in relation to the x-axis. The ability to convert a linear equation to slope-intercept form is a valuable skill, as it allows you to quickly identify the slope and y-intercept.

Coefficient of x

In algebra, the coefficient of \( x \) is the numerical factor that is multiplied by the variable \( x \). It plays a pivotal role in determining the slope of a line when the equation is in slope-intercept form, as seen in the example \( y = \frac{-x}{9} \).

• The coefficient of \( x \) in the slope-intercept form \( y = mx + b \) is the slope \( m \).
• If the coefficient of \( x \) is positive, the slope of the line will be positive, indicating an upward tilt from left to right.
• If it is negative, the slope will also be negative, indicating a downward tilt.
• A coefficient of \( 0 \) would mean that the line is horizontal with a slope of zero.

Knowing how to identify and interpret the coefficient of \( x \) in an equation is crucial for understanding the direction and steepness of the graphed line. It's also important when solving for the value of one variable in terms of the other, as it directly impacts the rate of change from one point to another on a straight line.