Problem 47 - Algebra 1

Question

Use a graphing calculator to approximate the solution of the equation. $$ 5 x^{2}+5 x-1=0 $$

Step-by-Step Solution

Answer

The solutions of the equation can be approximated using a graphing calculator. By graphing the given equation and determining where it intersects the x-axis, the solutions are obtained.

Step 1: Write the equation

The equation to solve is \( 5x^2 + 5x - 1 = 0 \)

Step 2: Graph the equation on a graphing calculator

Input the equation into the graphing calculator. This will result in a parabolic graph. Make sure all parts of the graph are visible by adjusting the window size and scale if necessary.

Step 3: Identify the x-intercepts

The solutions to the equation are the x-coordinates where the graph crosses the x-axis, also known as the x-intercepts.

Step 4: Obtain the solutions

Use the trace or zero feature of the calculator to find the exact coordinates of the x-intercepts. These are the solutions of the equation.

Key Concepts

Graphing Calculator

When approaching the task of solving quadratic equations, a graphing calculator is an indispensable tool. It allows you to visually interpret the equation by plotting it on a coordinate system. To use it effectively, first ensure that you have correctly entered the quadratic equation, in this case, 5x^2 + 5x - 1 = 0. Then, by manipulating the viewing window, you can observe the entire curve of the quadratic function to locate important features such as its vertex and intercepts. A graphing calculator not only provides a visual aid but can also calculate these intercepts using specific functions like 'zero' or 'intersect'.

Furthermore, the ability to observe the behavior of the parabola can aid in understanding concepts such as direction of opening, axis of symmetry, and the maximum or minimum values the function can take.

Parabolic Graph

A parabolic graph represents a quadratic function and always takes the shape of a parabola. This parabola can open upwards or downwards depending on the coefficient of the x^2 term. For the equation 5x^2 + 5x - 1 = 0, the positive coefficient indicates the parabola opens upwards. After graphing this equation on a calculator, you'll see a U-shaped curve.

The highest or lowest point, called the vertex, is crucial as it indicates the function's minimum or maximum value. In real-world applications, understanding the parabolic graph allows you to predict and optimize various outcomes, such as determining the maximum height a ball can reach when thrown into the air.

X-intercepts

The term x-intercepts refers to the points where the graph of an equation crosses the x-axis. These intercepts represent the solutions to the quadratic equation, as they satisfy the condition y = 0. When graphing our example 5x^2 + 5x - 1 = 0 on a graphing calculator, the x-intercepts are the points of interest to find the solutions of the equation.

In the context of a parabola, there can be zero, one, or two x-intercepts depending on how the curve interacts with the x-axis. Finding these points is often one of the main goals when solving quadratic equations, as they provide valuable information about possible real-world scenarios – such as the time at which a projectile lands back on the ground.

Quadratic Formula

If you're unable to use a graphing calculator or you want to verify the solutions you've graphed, the quadratic formula is a reliable alternative for solving quadratic equations. The formula is given by \( x = \frac{-b \pm \sqrt{b^2-4ac}}{2a} \), where \(a\), \(b\), and \(c\) are the coefficients from the quadratic equation in the standard form ax^2 + bx + c = 0. By substituting the values a=5, b=5, and c=-1 into the formula, you can calculate the exact values of x that solve the equation 5x^2 + 5x - 1 = 0.

Understanding and applying the quadratic formula emphasizes the interplay between the algebraic approach and the graphical analysis of quadratic equations, providing a comprehensive view of the solutions available.