Chapter 2: Problem 77
Sketch by hand the line that passes through the points \((1,-2)\) and \((3,2)\).
Short Answer
Expert verified
The line passing through the points can be sketched using the equation \(y = 2x - 4\).
Step by step solution
01
Calculate the Slope
To sketch a line through two points \((1, -2)\) and \((3, 2)\), first calculate the slope (m) using the formula \(m = \frac{y_2 - y_1}{x_2 - x_1}\). Plugging in the points, we have \(m = \frac{2 - (-2)}{3 - 1} = \frac{4}{2} = 2\). So, the slope of the line is 2.
02
Choose the Point-Slope Formula
Use the point-slope form of the equation to write the equation of the line. The formula is \(y - y_1 = m(x - x_1)\). We use the point \((1, -2)\) with the slope \(m = 2\).
03
Write the Equation of the Line
Substitute the point \((1, -2)\) and slope \(m = 2\) into the point-slope formula: \(y + 2 = 2(x - 1)\). Simplify this to get the standard form: \(y = 2x - 4\).
04
Plot the Points
On a coordinate plane, plot the given points \((1, -2)\) and \((3, 2)\). These points will guide the sketching of the line.
05
Draw the Line
Using a ruler, draw a straight line that passes through the two plotted points \((1, -2)\) and \((3, 2)\). Ensure that the line is straight and extends in both directions.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope Calculation
Understanding how to calculate the slope of a line is a vital skill in algebra. The **slope** of a line measures its steepness and direction. To find the slope between two points, \((x_1, y_1)\) and \((x_2, y_2)\), use the formula:
It's a simple subtraction between the \(y\) coordinates, divided by the subtraction of the \(x\) coordinates. With the points given, \((1, -2)\) and \((3, 2)\), we calculate:
- \( m = \frac{y_2 - y_1}{x_2 - x_1} \)
It's a simple subtraction between the \(y\) coordinates, divided by the subtraction of the \(x\) coordinates. With the points given, \((1, -2)\) and \((3, 2)\), we calculate:
- \( m = \frac{2 - (-2)}{3 - 1} = \frac{4}{2} = 2 \)
Point-Slope Form
The **point-slope form** of a linear equation is another way to represent a line using its slope and a point on the line. The formula is:
For example, with the point \((1, -2)\) and a slope \( m = 2 \), it translates to:
- \( y - y_1 = m(x - x_1) \)
For example, with the point \((1, -2)\) and a slope \( m = 2 \), it translates to:
- \( y + 2 = 2(x - 1) \)
Standard Form
Converting a line's equation from point-slope form to **standard form** is often beneficial for calculations. Standard form looks like this:
From our earlier point-slope equation, \( y + 2 = 2(x - 1) \), simplify to the following steps:
- \( Ax + By = C \)
From our earlier point-slope equation, \( y + 2 = 2(x - 1) \), simplify to the following steps:
- Distribute the \(2\): \( y + 2 = 2x - 2 \)
- Rearrange: \( y = 2x - 4 \)
Coordinate Plane
A **coordinate plane** is a two-dimensional surface on which we can plot points, lines, and curves to visualize algebraic equations. The coordinate plane is formed by two perpendicular number lines intersecting at the origin (0,0):
The line passing through the points \((1, -2)\) and \((3, 2)\) can be sketched by plotting these points on the graph. Each point identifies a specific position on the plane. Connecting these points with a straight line provides a visual representation of the equation \( y = 2x - 4 \). It effectively shows the slope and the path through multiple pairs that satisfy the equation.
- The horizontal axis is the x-axis.
- The vertical axis is the y-axis.
The line passing through the points \((1, -2)\) and \((3, 2)\) can be sketched by plotting these points on the graph. Each point identifies a specific position on the plane. Connecting these points with a straight line provides a visual representation of the equation \( y = 2x - 4 \). It effectively shows the slope and the path through multiple pairs that satisfy the equation.