Chapter 2: Problem 1
Find the gradient, \(m\), and \(y\)-intercept, \(c\), of the following graphs, and sketch them: a \(y=x+1\) b \(y=x-1\) c \(y=3 x+5\) d \(y=\frac{1}{2} x-7\) e \(y-\pi=0\) f \(y+\pi-x=0\)
Short Answer
Expert verified
a) m=1, c=1; b) m=1, c=-1; c) m=3, c=5; d) m=1/2, c=-7; e) m=0, c=Ï€; f) m=1, c=-Ï€
Step by step solution
01
- Understand the Slope-Intercept Form
The slope-intercept form of a linear equation is given by: \[ y = mx + c \]where \(m\) is the gradient (or slope) and \(c\) is the y-intercept.
02
- Analyze Equation a
The equation for part (a) is: \[ y = x + 1 \]Here, \(m = 1\) and \(c = 1\). Therefore, the gradient, \(m\), is 1 and the y-intercept, \(c\), is 1.
03
- Analyze Equation b
The equation for part (b) is: \[ y = x - 1 \]Here, \(m = 1\) and \(c = -1\). Therefore, the gradient, \(m\), is 1 and the y-intercept, \(c\), is -1.
04
- Analyze Equation c
The equation for part (c) is: \[ y = 3x + 5 \]Here, \(m = 3\) and \(c = 5\). Therefore, the gradient, \(m\), is 3 and the y-intercept, \(c\), is 5.
05
- Analyze Equation d
The equation for part (d) is: \[ y = \frac{1}{2}x - 7 \]Here, \(m = \frac{1}{2}\) and \(c = -7\). Therefore, the gradient, \(m\), is \( \frac{1}{2} \) and the y-intercept, \(c\), is -7.
06
- Analyze Equation e
The equation for part (e) is: \[ y - \pi = 0 \]Simplify to get: \[ y = \pi \]Here, there is no \(x\) term, so \(m = 0\) and \(c = \pi\). Therefore, the gradient, \(m\), is 0 and the y-intercept, \(c\), is \(\pi\).
07
- Analyze Equation f
The equation for part (f) is: \[ y + \pi - x = 0 \]Simplify to get: \[ y = x - \pi \]Here, \(m = 1\) and \(c = -\pi\). Therefore, the gradient, \(m\), is 1 and the y-intercept, \(c\), is -\pi.
08
- Sketch the Graphs
Using the gradients and y-intercepts found, draw each line on a coordinate plane. The slope (gradient) determines the angle of the line, and the y-intercept shows where the line crosses the y-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
Understanding the slope-intercept form is essential for identifying the gradient and the y-intercept in linear equations. The general format is given by: \[ y = mx + c \] Here, \(m\) represents the gradient (or slope) of the line, and \(c\) is the y-intercept where the line crosses the y-axis. When a linear equation is arranged in this form, it is easy to read off both the gradient and y-intercept values directly. For example, in the equation \(y = 2x + 3\), the gradient \(m\) is 2, and the y-intercept \(c\) is 3. Recognizing this format allows you to quickly interpret the characteristics of a linear graph.
Gradient
The gradient, also known as the slope, indicates how steep a line is. It is represented by the symbol \(m\) in the slope-intercept form equation \(y = mx + c\). The gradient can be positive, negative, zero, or undefined:
- A positive gradient means the line slopes upwards as you move from left to right.
- A negative gradient means the line slopes downwards as you move from left to right.
- A zero gradient means the line is horizontal.
- An undefined gradient means the line is vertical.
Y-Intercept
The y-intercept is where the line crosses the y-axis on a graph. It is represented by the symbol \(c\) in the slope-intercept form equation \(y = mx + c\). This value shows where the line intersects the y-axis when the value of \(x\) is zero. For example, in the equation \(y = x + 1\), the y-intercept \(c\) is 1. This means that the line crosses the y-axis at \(y = 1\). If we consider another equation \(y = 3x - 2\), the y-intercept \(c\) is -2, indicating the line crosses the y-axis at \(y = -2\). Knowing the y-intercept allows you to pinpoint the exact location where the line meets the y-axis, which is crucial for sketching the graph accurately.
Graphing Lines
Graphing lines requires a clear understanding of both the gradient and y-intercept. First, start by plotting the y-intercept on the coordinate plane. This is the point where the line crosses the y-axis. Next, use the gradient to determine the direction and slope of the line. For a gradient \(m\), this means starting from the y-intercept and moving up or down by \(m\) units while moving one unit horizontally. For instance, a line with gradient \(m = 2\) means moving up 2 units for every 1 unit moved to the right. Taking some examples from the initial exercise:
- For the equation \(y = x + 1\), the y-intercept is 1, and the gradient is 1. Start at (0, 1) and move up 1 unit for every 1 unit to the right.
- For \(y = 3x + 5\), start at (0,5) and move up 3 units for every 1 unit to the right.