Chapter 0: Problem 5
Graph each pair of equations on one set of axes. $$y=-2 x^{2} \text { and } y=-2 x^{2}+1$$
Short Answer
Expert verified
Graph \(y = -2x^2\) and \(y = -2x^2 + 1\). The first parabola is at \((0,0)\) and the second is at \((0,1)\).
Step by step solution
01
Understand the equations
Identify the given equations. The first equation is \(y = -2x^2\). The second equation is \(y = -2x^2 + 1\). Notice that these are both quadratic equations, and one is a simple vertical shift of the other.
02
Identify the vertex of each parabola
For the equation \(y = -2x^2\), the vertex is at the origin \((0,0)\). For the equation \(y = -2x^2 + 1\), the vertex is shifted up by 1 unit, so the vertex is at \((0, 1)\).
03
Determine the shape and direction of the parabolas
Both equations have the same coefficient for the \(x^2\) term, \(-2\), which means they open downward and are stretched vertically by a factor of \2\.
04
Plot key points
Choose key points to plot for each curve. For \(y = -2x^2\), plot points such as \((0,0)\), \((1, -2)\), and \((-1, -2)\). For \(y = -2x^2 + 1\), plot \((0,1)\), \((1, -1)\), and \((-1, -1)\).
05
Draw the parabolas
Graph the points and sketch each parabola. The parabola for \(y = -2x^2\) should pass through \((0,0)\), \((1,-2)\), and \((-1, -2)\). The parabola for \(y = -2x^2 + 1\) should pass through \((0,1)\), \((1,-1)\), and \((-1, -1)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic equations
Quadratic equations are polynomial equations of the form \(y = ax^2 + bx + c\). These equations are called quadratic because 'quad' means square, referring to the square of the variable \(x\). For the given equations, \(y = -2x^2\) and \(y = -2x^2 + 1\), notice the \(x^2\) term.
The 'a' coefficient tells us about the direction and shape of the parabola:
Here, both equations have \(a = -2\), so both parabolas open downward. The 'b' and 'c' coefficients change the position and shape depending on their values. But our equations lack an 'x' term (b=0), simplifying things.
The 'a' coefficient tells us about the direction and shape of the parabola:
- If 'a' is positive, the parabola opens upwards.
- If 'a' is negative, the parabola opens downwards.
Here, both equations have \(a = -2\), so both parabolas open downward. The 'b' and 'c' coefficients change the position and shape depending on their values. But our equations lack an 'x' term (b=0), simplifying things.
parabolas
A parabola is the graph of a quadratic equation. It's a symmetric, U-shaped curve. For the equations \(y = -2x^2\) and \(y = -2x^2 + 1\), they form parabolas.
Key properties include:
Since our 'a' is negative, both parabolas open downward. The vertex's y-coordinate shows the maximum point.
Key properties include:
- The vertex, the highest or lowest point (turning point).
- The axis of symmetry which passes through the vertex and divides the parabola into two mirror images.
- The direction in which it opens (up or down) determined by the sign of 'a'.
Since our 'a' is negative, both parabolas open downward. The vertex's y-coordinate shows the maximum point.
vertex shift
The vertex shift is how the vertex of the parabola moves from its typical position. For the standard quadratic equation \(y = ax^2\), the vertex is at (0,0). In our second equation, \(y = -2x^2 + 1\), the +1 means a vertical shift.
In the first equation, the vertex is at (0,0). In the second, it's at (0,1). Just add the constant to the original y-coordinate to find the new vertex position.
- When a constant is added (e.g., +1), the vertex moves up.
- When a constant is subtracted (e.g., -1), the vertex moves down.
In the first equation, the vertex is at (0,0). In the second, it's at (0,1). Just add the constant to the original y-coordinate to find the new vertex position.
plotting points
Plotting key points helps sketch accurate graphs of parabolas. Choose symmetrical points around the vertex. Here’s how:
Plot these points on your graph, then draw smooth curves connecting the points to form the parabolas. This method ensures accuracy and symmetry.
- Start with the vertex. For \(y = -2x^2\), it's (0,0). For \(y = -2x^2 + 1\), it's (0,1).
- Choose points on either side. For example, for \(y = -2x^2\), points like (1,-2) and (-1,-2).
- Do the same for the second equation. For \(y = -2x^2 + 1\), choose points like (1,-1) and (-1,-1).
Plot these points on your graph, then draw smooth curves connecting the points to form the parabolas. This method ensures accuracy and symmetry.