**The Vector Equation of Lines - Multivariable Calculus**

How much did John invest in each type of fund? Understanding the correct approach to setting up problems such as this one makes finding a solution a matter of following a pattern.

We will solve this and similar problems involving three equations and three variables in this section. Doing so uses similar techniques as those used to solve systems of two equations in two variables. However, finding solutions to systems of three equations requires a bit more organization and a touch of visual gymnastics.

In order to solve systems of equations in three variables, known as three-by-three systems, the primary tool we will be using is called Gaussian elimination, named after the prolific German mathematician Karl Friedrich Gauss.

While there is no definitive order in which operations are to be performed, there are specific guidelines as to what type of moves can be made. We may number the equations to keep track of the steps we apply. A system in upper triangular form looks like the following:.

To write the system in upper triangular form, we can perform the following operations:. Graphically, the ordered triple defines the point that is the intersection of three planes in space. You can visualize such an intersection by imagining any corner in a rectangular room. A corner is defined by three planes: two adjoining walls and the floor or ceiling. Any point where two walls and the floor meet represents the intersection of three planes.

In equations 4 and 5we have created a new two-by-two system.

## Linear equation

How much did he invest in each type of fund? To solve this problem, we use all of the information given and set up three equations. First, we assign a variable to each of the three investment amounts:. Step 1. Interchange equation 2 and equation 3 so that the two equations with three variables will line up. Step 2. Write the result as row 2.

Step 4. Just as with systems of equations in two variables, we may come across an inconsistent system of equations in three variables, which means that it does not have a solution that satisfies all three equations.

The equations could represent three parallel planes, two parallel planes and one intersecting plane, or three planes that intersect the other two but not at the same location.

In this system, each plane intersects the other two, but not at the same location. Therefore, the system is inconsistent.

We know from working with systems of equations in two variables that a dependent system of equations has an infinite number of solutions. The same is true for dependent systems of equations in three variables. An infinite number of solutions can result from several situations.

The three planes could be the same, so that a solution to one equation will be the solution to the other two equations. All three equations could be different but they intersect on a line, which has infinite solutions. Or two of the equations could be the same and intersect the third on a line.

We do not need to proceed any further. When a system is dependent, we can find general expressions for the solutions. Adding equations 1 and 3we have. The solution set is infinite, as all points along the intersection line will satisfy all three equations.In the applet below, lines can be dragged as a whole or with one of the two defining points. When a line is dragged or clicked upon, one of its equations is displayed just beneath the graph. With the Reduce box checked, the equation appears in its simplest form.

The applet can display several lines simultaneously. To obtain additional lines, check the Duplicate box and start dragging one of the already present lines to the desired position. In fact, you'll be dragging a newly created copy of that line. As ofJava plugins are not supported by any browsers find out more. This Wolfram DemonstrationTwo Points Determine a Lineshows an item of the same or similar topic, but is different from the original Java applet, named 'LinearFunc'. The originally given instructions may no longer correspond precisely.

Below I give several forms of the equation of a straight line depending on the attributes it is defined with. In every case, the verification is straightforward. Plug in the data and see that it satisfies the equation. All the equations below are derived in the usual Cartesian coordinate system.

The line through two distinct points x 1y 1 and x 2y 2 is given by. In case they are equal, the equation is simplified to. However, the simplest for me to remember is this. The latter interpretation shows that a straight line is the locus of points r with the property. That is a straight line is a locus of points whose radius-vector has a fixed scalar product with a given vector nnormal to the line.

To see why the line is normal to ntake two distinct but otherwise arbitrary points r 1 and r 2 on the line, so that. In other words the vector r 1 - r 2 that joins the two points and thus lies on the line is perpendicular to n.

Note that the line defined by a general equation would not change if the equation were to be multiplied by a non-zero coefficient. This property can be used to keep the coefficient A non-negative.

It can also be used to normalize the equation by dividing it by n. As a result, in a normalized equation. In the applet, the coefficients of the normalized equation are rounded to up to 6 digits, for which reason the above identity may only hold approximately. The normalized equation is conveniently used in determining the distance from a point to a line.

Assume a straight line intersects x-axis at a, 0 and y-axis at 0, b. Then it is defined by the equation. The latter form is somewhat more general as it allows either a or b to be 0. These are signed distances from the points of intersection of the line with the axes.By Deborah J. A regression line is simply a single line that best fits the data in terms of having the smallest overall distance from the line to the points. Statisticians call this technique for finding the best-fitting line a simple linear regression analysis using the least squares method.

The slope of a line is the change in Y over the change in X. For example, a slope of. The y-intercept is the value on the y-axis where the line crosses. The coordinates of this point are 0, —6 ; when a line crosses the y- axis, the x- value is always 0.

You may be thinking that you have to try lots and lots of different lines to see which one fits best. The standard deviation of the x values denoted s x.

The standard deviation of the y values denoted s y. You simply divide s y by s x and multiply the result by r. Note that the slope of the best-fitting line can be a negative number because the correlation can be a negative number.

A negative slope indicates that the line is going downhill. For example, if an increase in police officers is related to a decrease in the number of crimes in a linear fashion; then the correlation and hence the slope of the best-fitting line is negative in this case.

The correlation and the slope of the best-fitting line are not the same. The formula for slope takes the correlation a unitless measurement and attaches units to it. Think of s y divided by s x as the variation resembling change in Y over the variation in X, in units of X and Y. For example, variation in temperature degrees Fahrenheit over the variation in number of cricket chirps in 15 seconds.

So to calculate the y -intercept, bof the best-fitting line, you start by finding the slope, m, of the best-fitting line using the above steps. Then to find the y- intercept, you multiply m by. Always calculate the slope before the y- intercept. The formula for the y- intercept contains the slope! Deborah J. How to Calculate a Regression Line. Scatterplot of cricket chirps in relation to outdoor temperature. About the Book Author Deborah J.When an equation is in this form, the slope of the line is given by m and the y-intercept is located at b.

The following diagram shows an equation in slope-intercept form. Scroll down the page for more examples and solutions on how to use the slope-intercept form of an equation. The equation of a horizontal line is then in the form.

A vertical line has a slope that is undefined. Therefore, it cannot be written in slope-intercept form. Instead, the equation of a vertical line is in the form.

To find the equation of a line when given two points on the line, we first find the slope and then find the y-intercept. The slope is the ratio of the change in the y-value over the change in the x-value. Given any two points on a line, you can calculate the slope of the line by using this formula:. Step 3: Select one of the given points, for example 4, 1and substitute the x and y values into the equation. Try the free Mathway calculator and problem solver below to practice various math topics.

Try the given examples, or type in your own problem and check your answer with the step-by-step explanations. We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page. Slope and y-intercept of an equation Show Step-by-step Solutions.If you're seeing this message, it means we're having trouble loading external resources on our website.

To log in and use all the features of Khan Academy, please enable JavaScript in your browser. Donate Login Sign up Search for courses, skills, and videos. Math Algebra 1 Forms of linear equations Writing slope-intercept equations. Slope-intercept equation from graph. Writing slope-intercept equations. Practice: Slope-intercept equation from graph.

Slope-intercept equation from two points. Practice: Slope-intercept from two points. Constructing linear equations from context. Practice: Writing linear equations word problems. Slope-intercept form review. Next lesson. Current timeTotal duration Math: 8. Google Classroom Facebook Twitter. What is the equation of this line in slope-intercept form?

### Equation of Line

So any line can be represented in slope-intercept form, is y is equal to mx plus b, where this m right over here, that is of the slope of the line. And this b over here, this is the y-intercept of the line. Let me draw a quick line here just so that we can visualize that a little bit.

So that is my y-axis. And then that is my x-axis. And let me draw a line. And since our line here has a negative slope, I'll draw a downward sloping line. So let's say our line looks something like that.

So hopefully, we're a little familiar with the slope already. The slope essentially tells us, look, start at some point on the line, and go to some other point of the line, measure how much you had to move in the x direction, that is your run, and then measure how much you had to move in the y direction, that is your rise.

And our slope is equal to rise over run. And you can see over here, we'd be downward sloping. Because if you move in the positive x direction, we have to go down. If our run is positive, our rise here is negative. So this would be a negative over a positive, it would give you a negative number. That makes sense, because we're downward sloping. The more we go down in this situation, for every step we move to the right, the more downward sloping will be, the more of a negative slope we'll have.

So that's slope right over here. The y-intercept just tells us where we intercept the y-axis. So the y-intercept, this point right over here, this is where the line intersects with the y-axis. This will be the point 0 comma b.

And this actually just falls straight out of this equation. When x is equal to so let's evaluate this equation, when x is equal to 0.Solution: and since the point lies in the 3rd quadrant, then. As the polar equation of a line where p is the distance of the line from the pole O and j is the angle that the segment p makes with the polar axis. General equation of a circle in polar coordinates The general equation of a circle with a center at r 0j and radius R.

Polar equation of a circle with radius R and a center on the polar axis running through the pole O origin. Polar coordinate system. Polar and Cartesian coordinates relations. Lines parallel to the axes, horizontal and vertical lines. Lines parallel to the y -axis. Lines parallel to the x -axis. Lines running through the origin or pole radial lines. The equation of a line through the origin or pole that makes an angle a with the positive x -axis.

Polar equation of a line. Proof, using Cartesian to polar conversion formulas. The intercept form of the line. General equation of a circle in polar coordinates. The general equation of a circle with a center at. Using the law of cosine. Polar equation of a circle with a center on the polar axis running through the pole.

Polar equation of a circle with a center at the pole. Contents B. All rights reserved.A line of best fit is a straight line that is the best approximation of the given set of data.

It is used to study the nature of the relation between two variables. We're only considering the two-dimensional case, here.

## 7.3: Systems of Linear Equations with Three Variables

A line of best fit can be roughly determined using an eyeball method by drawing a straight line on a scatter plot so that the number of points above the line and below the line is about equal and the line passes through as many points as possible. A more accurate way of finding the line of best fit is the least square method. Use the following steps to find the equation of line of best fit for a set of ordered pairs x 1y 1x 2y 2Step 1: Calculate the mean of the x -values and the mean of the y -values.

Step 3: Compute the y -intercept of the line by using the formula:.

Step 4: Use the slope m and the y -intercept b to form the equation of the line. Use the least square method to determine the equation of line of best fit for the data. Then plot the line. Solution: Plot the points on a coordinate plane.

Calculate the means of the x -values and the y -values. Use the formula to compute the y -intercept. Use the slope and y -intercept to form the equation of the line of best fit. Names of standardized tests are owned by the trademark holders and are not affiliated with Varsity Tutors LLC. Media outlet trademarks are owned by the respective media outlets and are not affiliated with Varsity Tutors.

Varsity Tutors connects learners with experts. Instructors are independent contractors who tailor their services to each client, using their own style, methods and materials. Line of Best Fit Least Square Method A line of best fit is a straight line that is the best approximation of the given set of data. Example: Use the least square method to determine the equation of line of best fit for the data. Subjects Near Me. Louis Tutoring. Download our free learning tools apps and test prep books.

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