Question

Find the slope and the \(y\) -intercept (if possible) of the line. $$ x+5 y=20 $$

Short answer

The slope of the line is \(-1/5\) and the y-intercept is \(4\).

Step-by-step solution

Rearrange the equation

The equation to be rearranged is \(x+5y=20\). Converting this equation into the slope-intercept form involves isolating the \(y\) variable on one side. To do this, subtract \(x\) from both sides of the equation. This gives the equation \(5y= 20-x\).

Simplify the Equation

The equation is now \(5y = 20 - x\). To isolate \(y\), divide the entire equation by \(5\). This gives the slope-intercept form of the equation, \(y = -1/5x + 4\).

Identify Slope and Y-Intercept

The equation \(y = -1/5x + 4\) is now in slope intercept form. Here, the coefficient of \(x\) or \(-1/5\) is the slope and \(4\) is the \(y\)-intercept

Key concepts

Finding Slope

Understanding the slope of a line is fundamental when studying linear equations. The slope is a measure of how steep a line is, and it is defined as the ratio of the vertical change (rise) to the horizontal change (run) between two points on a line. In the slope-intercept form of a linear equation, which is written as \(y = mx + b\), the slope is represented by \(m\).

When you are given an equation like \(x + 5y = 20\), finding the slope involves rearranging the equation into slope-intercept form. You then easily identify the slope as the coefficient of the \(x\) term. In the example given, after isolating \(y\), the equation \( y = -\frac{1}{5}x + 4 \) shows that the slope of the line is \(-\frac{1}{5}\). This means that for each unit increase in \(x\), the value of \(y\) decreases by \(\frac{1}{5}\).

Y-intercept

The \(y\)-intercept is another crucial component of linear equations, representing the point where the line crosses the \(y\)-axis. When you look at the equation in its slope-intercept form \(y = mx + b\), the \(y\)-intercept is denoted by \(b\).

In the same equation we've been examining, \(y = -\frac{1}{5}x + 4\), the \(y\)-intercept is the constant term \(4\). This signifies that when \(x\) is equal to zero, the value of \(y\) will be \(4\), hence the line will cross the \(y\)-axis at the point \((0, 4)\). The \(y\)-intercept is an essential value because it provides a starting point from which you can graph the entire line.

Linear Equations

Linear equations form the basis for much of algebra and represent relationships with a constant rate of change. The standard form of a linear equation is \(Ax + By = C\), but for graphing and understanding the behavior of the line, the slope-intercept form \(y = mx + b\) is often more useful. It directly shows the slope and \(y\)-intercept of the line, as we've seen in the examples.

This form makes it clear that every linear equation graphs into a straight line and that the slope describes the direction and steepness of the line, while the \(y\)-intercept provides a specific point on the y-axis. To transform an equation from standard form to slope-intercept form, isolate \(y\) by performing algebraic operations as shown in steps of the example solution. It's a powerful skill that enables us to visualize and solve problems involving linear relationships effectively.