Chapter 0: Problem 30
Find an equation of the line: with \(m=-3,\) containing (5,-2).
Short Answer
Expert verified
The equation of the line is \(y = -3x + 13\).
Step by step solution
01
Write Down the Point-Slope Formula
The point-slope form of a linear equation is given by \(y - y_1 = m(x - x_1)\), where \((x_1, y_1)\) is a point on the line and \(m\) is the slope. For this problem, the point is \((5, -2)\) and the slope is \(m = -3\).
02
Substitute the Given Values
Substitute \((x_1, y_1) = (5, -2)\) and \(m = -3\) into the point-slope formula to get:\[y - (-2) = -3(x - 5)\].
03
Simplify the Equation
Simplify the expression to make it more readable:1. Simplifying the left side: \(y + 2\).2. Distribute \(-3\) in the right side: \(-3(x - 5) = -3x + 15\).Thus, the equation becomes: \[y + 2 = -3x + 15\].
04
Solve for y
To write the equation in slope-intercept form \(y = mx + b\), solve for \(y\):1. Subtract 2 from both sides: \[y = -3x + 15 - 2\].2. Simplify: \[y = -3x + 13\].This is the equation of the line.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Point-Slope Form
The point-slope form of a linear equation is a handy way to write the equation of a line when you know one point on the line and the slope. The generic formula is \(y - y_1 = m(x - x_1)\). Here, \((x_1, y_1)\) is the known point and \(m\) is the slope. This form is quite useful because it lets you plug in numbers directly when you have a point and the slope. You instantly get a linear equation, which is a straight line. In our example, the point is \((5, -2)\) and the slope is \(-3\).
- Substitute the point and slope into the formula: \(y - (-2) = -3(x - 5)\).
- It clearly shows how the line behaves around that point, with the slope showing steepness and direction.
Slope-Intercept Form
Slope-intercept form is another popular way to express the equation of a line. Its formula \(y = mx + b\) is intuitive and simple. Here, \(m\) is the slope and \(b\) is the y-intercept, which is the point where the line crosses the y-axis. This form is particularly useful for graphing because you can immediately see the starting point (the y-intercept) and how the line rises or falls with the slope.
- The slope tells us if the line goes up or down as we move from left to right.
- The y-intercept gives a neat starting point for plotting on a graph.
Gradient
The gradient, more commonly referred to as slope in the context of linear equations, indicates how steep a line is. It's a measure of the direction and steepness of a line. In mathematical terms, the slope \(m\) is the change in \(y\) divided by the change in \(x\), often illustrated as \(m = \frac{\Delta y}{\Delta x}\).
- A positive slope means the line rises as it moves from left to right.
- A negative slope means the line falls.
- A slope of zero means the line is flat, like a resting position.