Chapter 10: Problem 39
Identify the graph of the equation as a parabola (with vertical or horizontal axis), circle, ellipse, or hyperbola. $$4 x^{2}-16 x+9 y^{2}+36 y=-16$$
Short Answer
Expert verified
The equation represents an ellipse.
Step by step solution
01
Rewrite the Equation
Start by rewriting the given equation in a more standard form. The given equation is \(4x^2 - 16x + 9y^2 + 36y = -16\). First, we need to move the constant term to the right: \[4x^2 - 16x + 9y^2 + 36y + 16 = 0.\]
02
Complete the Square for x-terms
Focus on the \(x\)-terms: \(4x^2 - 16x\). Factor out the 4: \[4(x^2 - 4x).\] To complete the square, take half of the coefficient of \(x\), which is \(-4\), giving \(-2\). Square it to get 4, and write \((x-2)^2\) inside the parentheses: \[4((x-2)^2 - 4).\] Thus, this becomes \[4(x-2)^2 - 16.\]
03
Complete the Square for y-terms
Proceed with the \(y\)-terms: \(9y^2 + 36y\). Factor out the 9: \[9(y^2 + 4y).\] Take half of the coefficient of \(y\), which is 4, giving 2. Square it to get 4 and write \((y+2)^2\) inside the parentheses: \[9((y+2)^2 - 4).\] Thus, this becomes \[9(y+2)^2 - 36.\]
04
Combine and Simplify the Equation
Substitute back the completed squares into the equation: \[4(x-2)^2 - 16 + 9(y+2)^2 - 36 + 16 = 0.\] Simplify the equation: \[4(x-2)^2 + 9(y+2)^2 = 36.\]
05
Identify the Type of Conic
Now, focus on identifying the type of conic section. The equation \[ \frac{(x-2)^2}{9} + \frac{(y+2)^2}{4} = 1 \] is in the standard form of an ellipse (\(Ax^2 + By^2 = 1\) with positive coefficients for both variables). This confirms that the original equation represents an ellipse.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parabolas
A parabola is a symmetrical, open plane curve formed by the intersection of a cone with a plane parallel to its side. It can also be understood as the graph of a quadratic function, typically in the form of \[ y = ax^2 + bx + c \] Characteristics of parabolas include:
- They have a vertex, which is the highest or lowest point on the graph, depending on orientation.
- The axis of symmetry passes through the vertex, dividing the parabola into two mirror-image halves.
- They can open upwards, downwards, or sideways (left or right).
Circles
A circle, described by points equidistant from a center point, is a special type of an ellipse. Its general equation is given by: \[ (x - h)^2 + (y - k)^2 = r^2 \] where \((h, k)\) is the center and \(r\) is the radius.Key properties include:
- All points on the circle are the same distance from the center.
- The distance, known as the radius, remains constant.
- The circle is symmetric about its center point.
Ellipses
Ellipses are defined as squashed or stretched circles. They have the equation form:\[ \frac{(x-h)^2}{a^2} + \frac{(y-k)^2}{b^2} = 1 \] where \((h, k)\) is the center, \(a\) is the semi-major axis, and \(b\) is the semi-minor axis.Characteristics of an ellipse include:
- Two axes of symmetry: a major axis and a minor axis.
- Foci inside the ellipse where the sum of the distances from all points on the ellipse to each focus remains constant.
- Ellipses can look like circles when \(a=b\), but generally, the coefficients differ, providing the stretch.
Hyperbolas
Hyperbolas are conic sections formed by the intersection of a double cone with a plane in a manner that is neither parallel nor perpendicular to the cone's axis. Their standard form is:\[ \frac{(x-h)^2}{a^2} - \frac{(y-k)^2}{b^2} = 1 \]or\[ \frac{(y-k)^2}{b^2} - \frac{(x-h)^2}{a^2} = 1 \]where \((h, k)\) marks the center, and the \(a\) and \(b\) values help shape the hyperbola.Key features of hyperbolas are:
- Two branches, unlike other conics, each curving away from the center.
- Asymptotes, which are lines that the hyperbola approaches but never touches.
- Vertically or horizontally oriented, depending on the placement of terms.