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Give the slope and the \(y\)-intercept for each equation. a. \(y=-4-3 x\) b. \(2 x+7=y\) c. \(38 x-10 y=24\)

Short Answer

Expert verified
a. Slope: -3, Y-Intercept: -4 b. Slope: 2, Y-Intercept: 7 c. Slope: 3.8, Y-Intercept: -2.4

Step by step solution

01

Convert into Slope-Intercept Form (Equation a)

The first equation is given as \(y = -4 - 3x\). Reorder the terms to match the slope-intercept form \(y = mx + b\), where \(m\) is the slope and \(b\) is the \(y\)-intercept. Rewriting, we get \(y = -3x - 4\).
02

Identify Slope and Y-Intercept (Equation a)

From the equation \(y = -3x - 4\), we can directly identify the slope \(m = -3\) and the \(y\)-intercept \(b = -4\).
03

Convert into Slope-Intercept Form (Equation b)

Start with the equation \(2x + 7 = y\). It can be directly written in slope-intercept form as \(y = 2x + 7\), showing it is already in the correct form.
04

Identify Slope and Y-Intercept (Equation b)

Looking at \(y = 2x + 7\), the slope \(m = 2\) and the \(y\)-intercept \(b = 7\).
05

Convert Standard Form to Slope-Intercept Form (Equation c)

The equation is \(38x - 10y = 24\). We will rearrange this into the form \(y = mx + b\). Start by isolating \(y\) on one side: \(-10y = -38x + 24\). Divide all terms by \(-10\) to solve for \(y\): \(y = 3.8x - 2.4\).
06

Identify Slope and Y-Intercept (Equation c)

From the equation \(y = 3.8x - 2.4\), the slope \(m = 3.8\) and the \(y\)-intercept \(b = -2.4\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Equations
An equation is essentially a statement of equality between two expressions. It's like a balance scale; both sides need to be equal. In the context of algebra, equations are used to find unknown values, solve problems, and represent relationships between quantities. A linear equation specifically describes a straight line when graphed on a coordinate plane. Linear equations can often be written in the form of the slope-intercept equation:
  • Slope-Intercept Form: The general version of this is \( y = mx + b \), where:
  • \(y\) is the dependent variable,
  • \(x\) is the independent variable,
  • \(m\) represents the slope of the line,
  • \(b\) denotes the y-intercept, the point where the line crosses the y-axis.
Understanding equations is crucial because they model real-world situations. For instance, predicting costs, speed, or various outcomes in business and science all revolve around solving equations.
However, it's not just about the solutions. Thinking in terms of equations fosters better logical reasoning and problem-solving skills in general.
Algebra
Algebra is a branch of mathematics that deals with symbols and rules for manipulating those symbols. It allows us to express general relationships and solve problems involving variables that can have a range of values. Equations, like those in our exercise, are a fundamental part of algebra. They allow us to express relationships between quantities and to explore these relationships systematically.
One of the key tools in algebra is the ability to rearrange and simplify expressions to solve for unknowns. For example, turning an equation into the slope-intercept form involved rearranging terms to isolate \(y\) on one side, thus clarifying the relationship between variables. This is a common method used in algebra to make equations easier to understand and work with.
  • Variables: Symbols, often letters, that represent numbers or values we don't yet know.
  • Constants: Known values that don't change.
  • Operations: Basic mathematical processes like addition, subtraction, multiplication, and division.
  • Expressions: Combinations of variables, constants, and operations.
  • Functions: Special relationships where each input has only one output; often expressed using equations.
Algebra is all about finding these unknown values and understanding how different values relate to one another.
Linear Functions
A linear function is a specific type of function in mathematics that creates a straight line when graphed. The primary form of these functions is captured very well by the slope-intercept equation, \(y = mx + b\). Linear functions are notable because they represent very straightforward, constant relationships, which is why they're so frequently used in a range of fields—from economics to physics.
Every linear function includes:
  • The Slope: This represents the steepness of the line, calculated as the "rise over run," the change in \(y\) over the change in \(x\), thus \(m = \frac{\Delta y}{\Delta x}\).
  • The Y-Intercept: The specific point at which the line crosses the y-axis, denoted by \(b\). It indicates the value of \(y\) when \(x = 0\).
These elements make interpreting and graphing linear functions straightforward. By knowing the slope and intercept, you can quickly sketch the graph of the function on a coordinate plane.
The simplicity of linear functions is both their strength and limitation—they tell us precisely how one variable changes concerning another but do not account for more complex, variable relationships. In real-life situations, linear functions are ideal for modeling consistent, unchanging rates, like speed or growth.

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Most popular questions from this chapter

At 2:00 P.M, elevator A passes the second floor of the Empire State Building going up. The table shows the floors and the times in seconds after 2:00. \begin{tabular}{|l|c|c|c|c|c|c|c|} \hline Floor \(x\) & 2 & 4 & 6 & 8 & 10 & 12 & 14 \\ \hline Time after 2:00 (s) \(y\) & 0 & \(1.3\) & \(2.5\) & \(3.8\) & 5 & \(6.3\) & \(7.5\) \\\ \hline \end{tabular} a. What is the line of fit based on Q-points for the data? b. Give a real-world meaning for the slope. (a) c. About what time will this elevator pass the 60th floor if it makes no stops? (a) d. Where will this elevator be at \(2: 00: 45\) if it makes no stops?

For each of these tables of \(x\) - and \(y\)-values, decide if the values indicate a direct variation, an inverse variation, or neither. Explain how you made your decision. If the values represent a direct or inverse variation, write an equation. $$ \begin{aligned} &\begin{array}{|c|c|} \hline \text { a. } & \boldsymbol{x} \end{array}\\\ &\text { b. } \begin{array}{|c|c|} \hline \text { (a) } & \boldsymbol{y} \\ \hline-20 & -5 \\ \hline-8 & -12.5 \\ \hline 2 & 50 \\ \hline 10 & 10 \\ \hline 25 & 4 \\ \hline \end{array}\\\ &\text { c. } \begin{array}{|r|r|} \hline {}{}{\boldsymbol{x}} & {}{}{\boldsymbol{y}} \\ \hline 0 & 0 \\ \hline-6 & 15 \\ \hline 8 & -20 \\ \hline-12 & 30 \\ \hline 4 & -10 \\ \hline \end{array}\\\ &\text { d. }\\\ &\begin{array}{|r|c|} \hline {}{}{\boldsymbol{x}} & \boldsymbol{y} \\ \hline 78 & 6 \\ \hline 31.2 & 2.4 \\ \hline-145.6 & -11.2 \\ \hline 14.3 & 1.1 \\ \hline-44.2 & -3.4 \\ \hline \end{array} \end{aligned} $$

Your friend walks steadily away from you at a constant rate such that her distance at \(2 \mathrm{~s}\) is \(3.4 \mathrm{~m}\) and her distance at \(4.5 \mathrm{~s}\) is \(4.4 \mathrm{~m}\). Let \(x\) represent time in seconds, and let \(y\) represent distance in meters. a. What is the slope of the line that models this situation? (hi) b. What is the \(y\)-intercept of this line? Explain how you found it. c. Write a linear equation in intercept form that models your friend's walk.

Scoop has a rolling ice cream cart. He recorded his daily sales for the last seven days and the mean daytime temperature for each day. $$ \begin{aligned} &\text { Ice Cream Sales }\\\ &\begin{array}{|l|r|r|r|r|r|r|r|} \hline \text { Day } & 1 & 2 & 3 & 4 & 5 & 6 & 7 \\ \hline \text { Temperature ('F) } & 83 & 79 & 75 & 70 & 71 & 67 & 62 \\ \hline \text { Sales (cones) } & 66 & 47 & 51 & 23 & 33 & 30 & 21 \\ \hline \end{array} \end{aligned} $$ a. Find the equation of the line that passes through the points \((79,47)\) and \((67,30)\). (Use the second point as the point in the point-slope form.) (a) b. Graph the data and your line from 8 a on your calculator. Sketch the result. You should have noticed in \(8 \mathrm{~b}\) that the line does not fit the data well. In fact, no two points from this data set make a good model. In \(8 \mathrm{c}-\) e you'll adjust the values of \(y_{1}\) c. Copy the table shown, and begin by changing the value of \(y_{1}\). Write two new equations, one with a larger value for \(y_{1}\) and one Value with a smaller value for \(y_{1}\). Graph each equation, and describe how the graphs compare to your original equation. (a) d. Now write two new equations that have the same values of \(x_{1}\) and \(y_{1}\) as the original, but larger and smaller values of \(b\). Graph each equation, and describe how the graphs compare to your original equation. e. Continue to adjust your values for \(y_{1}\) and \(b\) until you find a line that fits the data well. Record your final equation, Graph your equation with the data and sketch the result.

Show the steps to solve each equation. Then use your calculator to verify your solution. a. \(8-12 m=17\) b. \(2 r+7=-24\) c. \(-6-3 w=42\)

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