Chapter 8: Problem 30
Find the \(x\) - and \(y\) -intercepts of the given curves. $$ x=t^{2}+t, y=t^{2}+t-6,-5 \leq t<5 $$
Short Answer
Expert verified
The \( x \)-intercept is \((6, 0)\) and the \( y \)-intercept is \((0, -6)\).
Step by step solution
01
Understand the Problem
We need to find the intercepts of the parametric equations for the given range of the parameter \( t \). The \( x \)-intercept is where the curve crosses the \( x \)-axis, and the \( y \)-intercept is where the curve crosses the \( y \)-axis.
02
Find the x-Intercepts
At the \( x \)-intercept, \( y = 0 \). Thus, set the equation for \( y \) to zero: \( t^2 + t - 6 = 0 \). Solve this quadratic equation to find the values of \( t \). Factoring gives: \( (t-2)(t+3) = 0 \). Therefore, \( t = 2 \) or \( t = -3 \). Substitute these values into the equation for \( x \) to get the \( x \)-coordinates of the intercepts: \( t = 2 \rightarrow x = 2^2 + 2 = 6 \) and \( t = -3 \rightarrow x = (-3)^2 - 3 = 6 \). So, the \( x \)-intercepts are \((6, 0)\) and \((6, 0)\); they collapse into a single point because they are the same.
03
Find the y-Intercepts
At the \( y \)-intercept, \( x = 0 \). Set the equation for \( x \) to zero: \( t^2 + t = 0 \). Solving this gives \( t(t+1) = 0 \), so \( t = 0 \) or \( t = -1 \). Substitute these \( t \)-values into the equation for \( y \) to find the \( y \)-coordinates of these intercepts: \( t = 0 \rightarrow y = 0^2 + 0 - 6 = -6 \) and \( t = -1 \rightarrow y = (-1)^2 + (-1) - 6 = -6 \). Therefore, the \( y \)-intercepts are \((0, -6)\) and \((0, -6)\); similarly, these intercepts merge into \((0, -6)\) due to their identity.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
x-intercepts
Finding the \( x \)-intercepts is all about locating where the curve hits the \( x \)-axis. At this point, the value of \( y \) will equal zero because the curve is not above or below the \( x \)-axis.To derive this in parametric equations, you set the \( y \)-equation to zero, allowing you to solve for \( t \). This particular exercise gives us the quadratic equation \( t^2 + t - 6 = 0 \). We factor it into \((t-2)(t+3) = 0\) to find \( t = 2 \) or \( t = -3 \).Using these \( t \)-values in the equation for \( x \), \( x=t^2+t \), helps us find the exact coordinates:
- For \( t = 2 \), \( x = 6 \).
- For \( t = -3 \), \( x = 6 \).
y-intercepts
The \( y \)-intercepts are points where the curve crosses the \( y \)-axis. Here, \( x \) is zero. To find these in parametric equations, you set the \( x \) equation equal to zero and solve for \( t \).In the problem, solving the equation \( t^2 + t = 0 \) resulting from \( x = 0 \) gives \( t = 0 \) or \( t = -1 \).Next, substituting back into the \( y \) equation \( y=t^2+t-6 \):
- For \( t = 0 \), \( y = -6 \).
- For \( t = -1 \), \( y = -6 \).
quadratic equation
Quadratic equations are polynomial equations of degree two and they appear as the standard form \( ax^2 + bx + c = 0 \). In this exercise, we see them in two different contexts due to parametric equations.For \( y=t^2+t-6 \), we set \( y=0 \) to solve for \( x \)-intercepts and get \( t^2 + t - 6 = 0 \). Factoring it gives \( (t-2)(t+3)=0 \), helping us find \( t \) values.Similarly, setting \( x=t^2 + t = 0 \), a simpler quadratic form, helps us find \( y \)-intercepts.What makes quadratics interesting is how every solution portrays a curve line shape or parabola. The solutions reflect critical points like the apex, intercepts, and crossing points. Understanding these allows us to pinpoint precisely where curves intersect the \( x \)- and \( y \)-axes in parametric equations.For this problem:
- Each solution determines how these parametric equations translate into the Cartesian plane.
- Solving the quadratic gives us specific parameter values that highlight various positions of the curve.