Chapter 29: Problem 7
In Exercises \(5-26,\) sketch the graphs of the given equations in the rectangular coordinate system in three dimensions. $$4 x-2 y+z-8=0$$
Short Answer
Expert verified
The plane intersects the x, y, and z axes at (2, 0, 0), (0, -4, 0), and (0, 0, 8), respectively.
Step by step solution
01
Understand the Equation Form
The given equation is a linear equation in three variables, representing a plane. It is written in the form: \( ax + by + cz + d = 0 \), where \( a = 4 \), \( b = -2 \), \( c = 1 \), and \( d = -8 \).
02
Find the X-intercept
To find the x-intercept, we set \( y = 0 \) and \( z = 0 \) in the equation and solve for \( x \). This gives us \( 4x - 8 = 0 \), thus \( x = 2 \). The x-intercept is \( (2, 0, 0) \).
03
Find the Y-intercept
To find the y-intercept, set \( x = 0 \) and \( z = 0 \) in the equation and solve for \( y \). This results in \( -2y - 8 = 0 \), so \( y = -4 \). The y-intercept is \( (0, -4, 0) \).
04
Find the Z-intercept
To find the z-intercept, set \( x = 0 \) and \( y = 0 \) in the equation and solve for \( z \). The equation simplifies to \( z - 8 = 0 \), thus \( z = 8 \). The z-intercept is \( (0, 0, 8) \).
05
Sketch the Plane Using Intercepts
Plot the intercepts found: \((2, 0, 0)\), \((0, -4, 0)\), and \((0, 0, 8)\) in a three-dimensional coordinate system. Draw lines connecting these intercepts to sketch the plane. In a 3D plot, these points form a triangle which is part of the plane.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Linear equations in 3D
Linear equations in a three-dimensional coordinate system express the relationship between three variables. In general, these equations are written in the form \( ax + by + cz + d = 0 \). When written like this, each component after the coefficients (\(a, b, c\)) represents a distinct variable (\(x, y, z\)).
These equations represent planes rather than lines, as they would in two dimensions. This means they describe a flat surface extending infinitely in all directions within the 3D space.
These equations represent planes rather than lines, as they would in two dimensions. This means they describe a flat surface extending infinitely in all directions within the 3D space.
- The coefficient \(a\) dictates the influence of the \(x\) variable on the plane.
- Similarly, \(b\) and \(c\) affect the influence of \(y\) and \(z\) variables respectively.
- The constant \(d\) determines the plane's position relative to the origin of the coordinate system.
Intercepts in 3D
Intercepts in a 3D coordinate system are where a plane meets the coordinate axes. Finding intercepts for a 3D equation follows a similar process to that of 2D equations. However, instead of two intercepts (x and y), we find three:
- **X-intercept:** Set \(y = 0\) and \(z = 0\), then solve for \(x\). The solution is where the plane intersects the x-axis.
- **Y-intercept:** Set \(x = 0\) and \(z = 0\), then solve for \(y\). This is where the plane meets the y-axis.
- **Z-intercept:** Set \(x = 0\) and \(y = 0\), then solve for \(z\). This shows the intersection on the z-axis.
Graphing planes
Graphing planes in a 3D coordinate system can seem daunting at first, but understanding intercepts makes it more manageable. Once you've found the intercepts:
When you're graphing a plane, the triangle formed by intercepts is part of an infinite plane, extending beyond these initial points. The triangle merely provides a starting glimpse, helpful for understanding the plane's orientation and slope.
- Plot each intercept on the corresponding axis within the 3D space.
- Draw lines between each set of intercepts. These lines show where the plane touches each axis and helps to create a visual framework of the plane.
- The result is a triangular outline, which is a part of the plane in the coordinate system.
When you're graphing a plane, the triangle formed by intercepts is part of an infinite plane, extending beyond these initial points. The triangle merely provides a starting glimpse, helpful for understanding the plane's orientation and slope.