Chapter 10: Problem 62
Find the points of intersection of \(x^{2}+4 y^{2}=20\) and \(x+2 y=6\)
Short Answer
Expert verified
The intersection points are (4, 1) and (2, 2).
Step by step solution
01
Identify Equations
The problem provides two equations. The first equation is a conic section: \(x^2 + 4y^2 = 20\), which is an ellipse. The second equation is linear: \(x + 2y = 6\). Our task is to find the points where these two curves intersect.
02
Solve the Linear Equation for x
Start by isolating \(x\) in the second equation \(x + 2y = 6\). Solve for \(x\) to express it in terms of \(y\):\[x = 6 - 2y\].
03
Substitute into the Quadratic Equation
Replace \(x\) in the first equation \(x^2 + 4y^2 = 20\) with the expression found in Step 2, \(6 - 2y\). This gives us:\[(6 - 2y)^2 + 4y^2 = 20\].
04
Expand and Simplify
Expand \((6 - 2y)^2\) to get \(36 - 24y + 4y^2\). Substitute this back into the equation to get:\[36 - 24y + 4y^2 + 4y^2 = 20\]. Combine like terms to obtain:\[8y^2 - 24y + 36 = 20\].
05
Rearrange into a Standard Quadratic Equation
Subtract 20 from both sides of the equation to get:\[8y^2 - 24y + 16 = 0\]. Divide the entire equation by 8 to simplify:\[y^2 - 3y + 2 = 0\].
06
Factor the Quadratic
The equation \(y^2 - 3y + 2 = 0\) can be factored into:\[(y - 1)(y - 2) = 0\]. This gives two potential solutions for \(y\), which are \(y = 1\) and \(y = 2\).
07
Find Corresponding x-values
Use the expression \(x = 6 - 2y\) to find the corresponding \(x\) values for each \(y\).For \(y = 1\), \(x = 6 - 2(1) = 4\).For \(y = 2\), \(x = 6 - 2(2) = 2\).
08
Intersection Points
The two points of intersection are \((4, 1)\) and \((2, 2)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ellipse Equations
An ellipse is a type of conic section, which is a curve obtained by intersecting a cone with a plane. The standard form of an ellipse equation is \[\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1\], where \(a\) and \(b\) are the lengths of the semi-major and semi-minor axes respectively. When these axes are equally distributed around the origin, they define the size and shape of the ellipse.
- The equation given in the exercise is \(x^2 + 4y^2 = 20\). By dividing everything by 20, it can be rewritten as \(\frac{x^2}{20} + \frac{y^2}{5} = 1\).
- This indicates an ellipse with a semi-major axis of \(\sqrt{20}\) and a semi-minor axis of \(\sqrt{5}\). The longer axis is along the x-direction, indicating the ellipse is wider than it is tall.
Linear Equations
Linear equations represent straight lines. They can be expressed in many forms, with the most common being the slope-intercept form \(y = mx + c\), where \(m\) is the slope and \(c\) is the y-intercept.In this exercise, the linear equation \(x + 2y = 6\) is given. It provides a direct, simple relationship between \(x\) and \(y\). This can also be rearranged to the form \(y = -\frac{1}{2}x + 3\), showing:
- A slope of -\(\frac{1}{2}\), indicating that for every 1 unit increase in \(x\), \(y\) decreases by \(0.5\).
- The y-intercept is 3, meaning the line crosses the y-axis at (0,3).
Quadratic Factoring
Quadratic factoring involves expressing a quadratic equation as a product of its factors. For a quadratic in the form \(ax^2 + bx + c = 0\), factoring can simplify solving. In this context, the equation \(y^2 - 3y + 2 = 0\) was obtained after rearranging and simplifying from the intersecting ellipse and line equations. The factors are:
- \((y - 1)(y - 2) = 0\), indicating solutions \(y = 1\) and \(y = 2\).
- These factors provide potential values for \(y\) that satisfy both initial equations simultaneously.
Conic Sections
Conic sections are the curves obtained by intersecting a plane with a double-napped cone. They include shapes such as circles, ellipses, parabolas, and hyperbolas.
Each conic section has a distinct set of properties and equations that describe their curves.
- Circles are a special type of ellipse with equal semi-major and semi-minor axes.
- Ellipses result when the intersection of the plane and the cone is such that it completely passes through one nap but not the other.
- Parabolas are formed when the plane is parallel to one of the generating lines of the cone.
- Hyperbolas result when the plane intersects both naps.