Chapter 0: Problem 9
Sketching a Graph by Point Plotting In Exercises \(7-16,\) sketch the graph of the equation by point plotting. \(y=4-x^{2}\)
Short Answer
Expert verified
Once plotted, the graph forms a downward opening parabola that passes through points (-2,0), (-1,3), (0,4), (1,3), and (2,0).
Step by step solution
01
Understand the Equation Type
The given equation is \(y = 4 - x^{2}\). This is a quadratic equation and its graph will be a parabola. The negative sign attached to the \(x^{2}\) term indicates that the parabola opens downwards.
02
Choose the Points to Plot
Select a few values for \(x\) and calculate the corresponding values for \(y\). It's always a good idea to include \(x = 0\) in the chosen values. For continuity and symmetry, it is also a good idea to pick both positive and negative values. For this exercise, let's choose \(x=-2, -1, 0, 1, 2\). Now calculate \(y\) for each point: for \(x = -2\), \(y = 4 - (-2)^{2} = 0\); for \(x = -1\), \(y = 4 - (-1)^{2} = 3\); for \(x = 0\), \(y = 4 - 0 = 4\); for \(x = 1\), \(y = 4 - (1)^{2} = 3\); and for \(x = 2\), \(y = 4 - (2)^{2} = 0\). So, the points to be plotted are (-2,0), (-1,3), (0,4), (1,3), and (2,0).
03
Plot the Points
Mark these points on the coordinate plane. After marking the points, simply draw a soft line that best fits these points. Since it's a quadratic equation, you should form the shape of a parabola
04
Analyze the Graph
Ensure that the graphed parabola opens downward (a property of quadratic equations with a negative \(x^{2}\) coefficient) and touches the points plotted earlier.
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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 mathematical expressions of the form \( ax^2 + bx + c = 0 \). They represent second-degree polynomials because the highest power of the variable \( x \) is squared. In quadratic equations, \( a \), \( b \), and \( c \) are constants with \( a \) not equal to zero. This distinguishes quadratics from linear equations.
- The standard form of a quadratic equation is \( y = ax^2 + bx + c \).
- If \( a > 0 \), the parabola opens upwards, and if \( a < 0 \), it opens downwards.
- The solutions or "roots" of quadratic equations can be found using the quadratic formula: \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \).
Graph Sketching
Graph sketching involves visually representing the relationship between variables by marking points on a coordinate plane. It helps to understand how changes in one variable affect another. The process usually involves:
- Identifying the type of equation you are working with - in our case, a quadratic equation.
- Selecting a range of \( x \)-values to calculate corresponding \( y \)-values.
- Plotting the calculated points on a graph.
- Drawing a smooth curve through the plotted points to complete the sketch.
Parabola
A parabola is the U-shaped graph formed by a quadratic equation. Specifically, it is the graph of a function set by \( y = ax^2 + bx + c \). Parabolas have distinctive features:
- Vertex: The highest or lowest point on the graph, depending on whether it opens downward or upward. In the equation \( y = 4 - x^2 \), the vertex is the point (0, 4).
- Axis of Symmetry: A vertical line that divides the parabola into two mirror-image halves. For \( y = 4 - x^2 \), this is the line \( x = 0 \).
- Direction: If the coefficient of \( x^2 \) is negative, the parabola opens downward, like in our example.
- Intercepts: Points where the parabola intersects the axes, such as the x-intercepts at (-2,0) and (2,0) or the y-intercept at (0,4).