Chapter 5: Problem 56
Solve each equation by graphing. If exact roots cannot be found, state the consecutive integers between which the roots are located. \(0=-x^{2}-4 x+5\)
Short Answer
Expert verified
Roots are between -5 and -4, and between 0 and 1.
Step by step solution
01
Rewrite the Equation into Standard Form
Start with the given equation: \[ 0 = -x^2 - 4x + 5 \] To make it easier to graph, rewrite this in standard quadratic form, which is \[ y = ax^2 + bx + c \] Here, we have \[ y = -x^2 - 4x + 5 \] Now it's ready to graph.
02
Identify Quadratic Properties
Identify the components of the quadratic equation that will help with graphing:- The quadratic coefficient (\( a \)) is \(-1\), indicating the parabola opens downwards.- The vertex form is not directly given, but from \( ax^2 + bx + c \), it's clear the equation is already set.- The \( y \)-intercept is at \( (0, 5) \) since when \( x = 0 \), \( y = 5 \).
03
Graph the Parabola
Plot the graph of the equation \( y = -x^2 - 4x + 5 \) using its properties:- Start from the \( y \)-intercept (0, 5).- Since the parabola opens downwards, and knowing it’s symmetric about the vertex line, plot additional points. - Alternatively, use graphing software or graph paper to ensure a smooth curve.
04
Identify Roots of the Equation
The roots of the equation are the \( x \)-values where \( y = 0 \) (i.e., where the graph intersects the \( x \)-axis):- By visual inspection of the graph, identify that these points lie between \(-5 \leq x \leq -3 \) and \( 1 \leq x \leq 3 \).
05
Confirm the Consecutive Interval
Estimate the locations further by observing where the parabola dips below the \( x \)-axis:- From inspection, confirm the roots lie between \(-5 \) and \(-4 \), as well as between \( 0 \) and \( 1 \). These are the intervals where the expression likely goes from positive to negative and vice versa.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Quadratics
Graphing a quadratic equation is a visual way of finding its roots. The standard form of a quadratic equation is given as \( y = ax^2 + bx + c \). This specific equation, \( y = -x^2 - 4x + 5 \), involves a few critical steps for graphing.
- Identify the quadratic term (\( ax^2 \)): Here, \( a = -1 \), which tells us that the parabola opens downwards.
- Plot the y-intercept, where \( x = 0 \): In our example, it's at (0, 5).
- Draw the parabola, using symmetry around its vertex to ensure the graph is accurate.
- For more precise parabolas, equidistant points from the vertex can be calculated and plotted.
Quadratic Roots
Quadratic roots are the values of \( x \) where the graph crosses the x-axis. These are the solutions to the equation \( ax^2 + bx + c = 0 \).
In our equation, the roots are where \( y = 0 \), so we find when \( -x^2 - 4x + 5 = 0 \). These intersections are critical:
In our equation, the roots are where \( y = 0 \), so we find when \( -x^2 - 4x + 5 = 0 \). These intersections are critical:
- For exact values, observe the x-coordinates at which the parabola intersects the x-axis.
- If graphing visually (without calculations), estimate the range by identifying the closes points where the parabola approaches the x-axis.
- Using a software tool or closely analyzing the graph can provide a more accurate estimation of the roots.
- Our graph shows these points fall approximately between \(-5\) and \(-4\), and between \(0\) and \(1\).
Parabola Properties
The properties of a parabola are derived from its quadratic equation and help understand its shape and behavior.
The equation \( y = -x^2 - 4x + 5 \) shows key traits through its components:
The equation \( y = -x^2 - 4x + 5 \) shows key traits through its components:
- Direction: The parabola opens downwards since the coefficient of \( x^2 \) is negative.
- Vertex: Though not calculated here, the vertex can be found using the formula \( x = -\frac{b}{2a} \).
- Y-Intercept: This is the point where the parabola crosses the y-axis, at (0, 5).
- Symmetry: The parabola is symmetric about the vertical line passing through the vertex.