Chapter 0: Problem 23
Find the point \((s)\) of intersection of the graphs of the functions. Express your answers accurate to five decimal places. $$ f(x)=0.3 x^{2}-1.7 x-3.2 ; \quad g(x)=-0.4 x^{2}+0.9 x+6.7 $$
Short Answer
Expert verified
The points of intersection are approximately \(s_1 ≈ (2.40018, -4.78686)\) and \(s_2 ≈ (-1.97155, 7.38055)\).
Step by step solution
01
Set f(x) equal to g(x)
To find the x-coordinate(s), set the two functions equal to each other:
\(0.3x^2 - 1.7x - 3.2 = -0.4x^2 + 0.9x + 6.7\)
02
Simplify the equation
Combine like terms to simplify the equation:
\(0.7x^2 - 2.6x - 9.9 = 0\)
03
Solve for x-coordinates using the Quadratic Formula
Use the Quadratic Formula to solve for x:
\(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\)
In the equation \(0.7x^2 - 2.6x - 9.9 = 0\), we have \(a = 0.7, b = -2.6\), and \(c = -9.9\). Plug these values into the Quadratic Formula:
\(x =\frac{2.6 \pm \sqrt{(-2.6)^2 - 4(0.7)(-9.9)}}{2(0.7)}\)
04
Calculate the x-coordinates
Evaluate the expression to find the x-coordinates:
\(x =\frac{2.6 \pm \sqrt{6.76 + 27.72}}{1.4}\)
\(x =\frac{2.6 \pm \sqrt{34.48}}{1.4}\)
Approximating the x-coordinates up to five decimal places, we get:
\(x_1 ≈ 2.40018\)
\(x_2 ≈ -1.97155\)
05
Calculate the y-coordinates
Use either function to find the corresponding y-coordinates. We will use the function f(x):
\(y_1 = f(x_1) = 0.3(2.40018)^2 -1.7(2.40018) -3.2\)
\(y_1 ≈ -4.78686\)
\(y_2 = f(x_2) = 0.3(-1.97155)^2 -1.7(-1.97155) -3.2\)
\(y_2 ≈ 7.38055\)
06
Write the points of intersection
The points of intersection are:
\(s_1 ≈ (2.40018, -4.78686)\)
\(s_2 ≈ (-1.97155, 7.38055)\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Functions
Functions in mathematics represent an important concept where each input is associated with a single output. Think of a function as a machine that takes an input, performs a specific task, and produces an output. In this exercise, we have two functions:
- The function \( f(x) = 0.3x^2 - 1.7x - 3.2 \) represents a parabola that opens upwards due to the positive coefficient of \( x^2 \).
- The function \( g(x) = -0.4x^2 + 0.9x + 6.7 \) is another parabola, but it opens downwards because the coefficient of \( x^2 \) is negative.
Intersection Points
Intersection points occur where two graphs meet. These points represent the values of \( x \) and \( y \) that satisfy both equations simultaneously. In our problem, we are looking for these intersection points by setting \( f(x) = g(x) \). This creates an equation that we need to solve to find the \( x \)-coordinates. Once we find the \( x \)-coordinates, we plug them back into one of the original functions to find the corresponding \( y \)-coordinates. These coordinates together form the intersection points.
- The intersection point \( s_1 ≈ (2.40018, -4.78686) \) shows where both functions have the same value.
- The point \( s_2 ≈ (-1.97155, 7.38055) \) represents another intersection point where the two equations are equal.
Quadratic Formula
The Quadratic Formula is a powerful tool used to solve equations of the form \( ax^2 + bx + c = 0 \). It provides an exact solution for any quadratic equation, making it essential for solving intersection problems involving parabolas. The formula is given by:\[{x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}}\]In this problem, the equation \( 0.7x^2 - 2.6x - 9.9 = 0 \) needs to be solved using the Quadratic Formula.
- Identify the coefficients: \( a = 0.7 \), \( b = -2.6 \), \( c = -9.9 \).
- Calculate the discriminant \( b^2 - 4ac \) to check the nature of the roots, which in this case is positive, indicating two real solutions.
- Plug the values into the formula to find \( x_1 \) and \( x_2 \), which lead to the intersection points.
Graphs
Graphs visually represent functions, making them a great tool for analyzing and understanding the behavior of equations. Each function can be plotted on a coordinate plane, with the \( x \)-axis representing the input and the \( y \)-axis representing the output.
- The graph of \( f(x) = 0.3x^2 - 1.7x - 3.2 \) will appear as a U-shaped curve due to its upward-opening parabola.
- The graph of \( g(x) = -0.4x^2 + 0.9x + 6.7 \) forms an arch or downward opening parabola.