Chapter 3: Problem 29
Write the slope-intercept equation of the line that passes through the given points.$$(1,-5),(3,-11)$$
Short Answer
Expert verified
The slope-intercept equation of the line that passes through the points (1, -5) and (3, -11) is y = -3x - 2.
Step by step solution
01
Calculate the Slope (m)
To find the slope of the line, use the formula (y2 - y1) / (x2 - x1). Here, we have two points (1, -5) and (3, -11). We can refer to (1, -5) as (x1, y1) and (3, -11) as (x2, y2). Applying the formula, we calculate the slope (m) as (-11 - (-5)) / (3 - 1) = -6 / 2 = -3.
02
Substitute for m, x, and y in the Slope-Intercept Equation
After finding the slope (m), we can substitute m, x, and y from one of the given points into the slope-intercept form (y = mx + b). Let's use the point (1, -5) for x and y. This requires calculating -5 = -3*1 + b.
03
Calculate the Y - Intercept (b)
By performing the calculations in the equation from step 2, we can calculate b. This gives us -5 = -3 + b, or b = -5 + 3 = -2. Thus, our y-intercept (b) is -2.
04
Write the Equation of the Line in Slope-Intercept Form
Finally, we can write the equation of the line in slope-intercept form (y = mx + b) by substituting the slope (m) and the y-intercept (b) that we found in the previous steps. This gives us the equation y = -3x - 2.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Calculating Slope
When it comes to finding the equation of a line, calculating the slope is the first crucial step. The slope determines how steep a line is and its direction—whether it inclines upwards or downwards as it moves from left to right. To calculate the slope, use the formula:
- \( m = \frac{y_2 - y_1}{x_2 - x_1} \)
- \((x_1, y_1)\), the coordinates of the first point, and
- \((x_2, y_2)\), the coordinates of the second point.
- \( m = \frac{-11 - (-5)}{3 - 1} = \frac{-6}{2} = -3 \)
Y-Intercept
The y-intercept is the point where the line crosses the y-axis on a graph. This is an essential part of the slope-intercept equation, which helps us describe the line completely.To find the y-intercept, we begin with the slope-intercept formula:
- \( y = mx + b \)
- \(-5 = -3 \cdot 1 + b \)
- Simplifying gives us: \( b = -5 + 3 = -2 \)
Equation of a Line
Once we have both the slope and the y-intercept, we can write the equation of the line. This equation represents all points on that line and gives us a quick way to understand its behavior.Using the slope \(m = -3\) and y-intercept \(b = -2\), insert these into the slope-intercept form:
- \( y = mx + b \)
- \( y = -3x - 2 \)
Linear Equations
Linear equations like \(y = mx + b\) are vital in mathematics because they describe straight lines, which are the simplest type of graph. These equations are used in various real-world applications, such as physics, economics, and everyday planning.Key aspects of linear equations include:
- The slope \(m\) impacts how steep or flat the line is, determining the rate of change.
- The y-intercept \(b\) tells us where the line crosses the y-axis, setting a baseline for the line's position.