Chapter 10: Problem 6
Eliminate the parameter and then sketch the curve. $$x=t^{2}+3 t, \quad y=t-2$$
Short Answer
Expert verified
The curve is a sideways parabola: \(x = y^2 + 7y + 10\).
Step by step solution
01
Express t in Terms of y
The given equation for \(y\) is \(y = t - 2\). Solve this expression for \(t\) in terms of \(y\): \[ t = y + 2 \]
02
Substitute t in the x Equation
Substitute \(t = y + 2\) into the equation for \(x\):\[ x = (y + 2)^2 + 3(y + 2) \]
03
Expand and Simplify
Expand the expression and simplify it:\[ (y + 2)^2 = y^2 + 4y + 4 \]Now substitute this:\[ x = y^2 + 4y + 4 + 3y + 6 \]Simplify further:\[ x = y^2 + 7y + 10 \]
04
Sketch the Curve
The expression \(x = y^2 + 7y + 10\) represents a quadratic equation in \(y\) with respect to \(x\). This is a parabola opening horizontally. To sketch it, recognize its vertex form by completing the square, or plot points for several \(y\) values to find corresponding \(x\) values.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Curve Sketching
Curve sketching involves drawing a graph representing a function or equation. To sketch a curve accurately, it's essential to understand the equation type you're working with. In our exercise, after eliminating the parameter, we end up with a quadratic equation in terms of \(y\).
A quadratic equation of the form \(x = ay^2 + by + c\) represents a parabola. Depending on how the terms are arranged, the parabola may open upwards, downwards, or sideways. In this case, since \(x\) is expressed as a function of \(y\), the parabola opens horizontally.
To sketch the curve:
A quadratic equation of the form \(x = ay^2 + by + c\) represents a parabola. Depending on how the terms are arranged, the parabola may open upwards, downwards, or sideways. In this case, since \(x\) is expressed as a function of \(y\), the parabola opens horizontally.
To sketch the curve:
- Identify the vertex: This is the point where the parabola changes direction. You can use completing the square or derivative methods to find it.
- Determine intercepts: These are the points where the graph crosses the axes.
- Plot additional points: Choose values for \(y\) and calculate corresponding \(x\) using the equation.
Quadratic Equations
Quadratic equations are polynomial equations of the second degree. They typically take the form \(ax^2 + bx + c = 0\) when \(x\) is the variable, although in our case, \(x\) and \(y\) switch roles.
Key characteristics of quadratic equations include:
Key characteristics of quadratic equations include:
- A parabolic graph: Quadratic equations always create a parabolic shape.
- Two possible solutions: These are called roots and can be found using the quadratic formula.
- A vertex, which represents the maximum or minimum point of the parabola.
Elimination of Parameter
The elimination of parameter is a process used to convert parametric equations into a single equation. This technique helps in sketching curves or simplifying the study of a motion path described by parameters.
For this technique, you must:
For this technique, you must:
- Solve the parameter equation: Express one variable in terms of the parameter.
- Substitute: Replace the parameter in the other equation to express one variable solely in terms of the other.