Finding the Intersections of the Two Functions

Oct 13, 2025 by wbrum.org 89 views

The Equation of a Quadratic Function: Finding the Values of a, b, and c

The equation $a x^2 + b x + c = 0$ is a quadratic equation, which can be solved using various methods such as factoring, completing the square, or using the quadratic formula. However, in this article, we will explore a unique approach to solving the equation by finding the intersections of two functions. We will use the functions $y = 3 x^2 - 2 x - 1$ and $y = 5 - 4 x$ to find the values of $a, b$ , and $c$ .

Understanding the Problem

To solve the equation $a x^2 + b x + c = 0$ graphically, we need to find the intersections of the two functions $y = 3 x^2 - 2 x - 1$ and $y = 5 - 4 x$ . The intersection points of these two functions will give us the solutions to the equation. We can then use these solutions to find the values of $a, b$ , and $c$ .

Finding the Intersections of the Two Functions

To find the intersections of the two functions, we need to set them equal to each other and solve for $x$ . This will give us the x-coordinates of the intersection points. We can then substitute these x-coordinates into one of the functions to find the corresponding y-coordinates.

Let's set the two functions equal to each other:

3 x^2 - 2 x - 1 = 5 - 4 x

Simplifying the equation, we get:

3 x^2 + 2 x - 6 = 0

This is a quadratic equation in the form $ax^2 + bx + c = 0$ . We can solve this equation using the quadratic formula:

x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

In this case, $a = 3$ , $b = 2$ , and $c = -6$ . Plugging these values into the quadratic formula, we get:

x = \frac{-2 \pm \sqrt{2^2 - 4(3)(-6)}}{2(3)}

Simplifying the equation, we get:

x = \frac{-2 \pm \sqrt{76}}{6}

This gives us two possible values for $x$ : $x = \frac{-2 + \sqrt{76}}{6}$ and $x = \frac{-2 - \sqrt{76}}{6}$ .

Finding the Values of a, b, and c

Now that we have found the x-coordinates of the intersection points, we can substitute these values into one of the functions to find the corresponding y-coordinates. Let's use the function $y = 3 x^2 - 2 x - 1$ .

Substituting $x = \frac{-2 + \sqrt{76}}{6}$ into the function, we get:

y = 3 \left(\frac{-2 + \sqrt{76}}{6}\right)^2 - 2 \left(\frac{-2 + \sqrt{76}}{6}\right) - 1

Simplifying the equation, we get:

y = \frac{3(-2 + \sqrt{76})^2}{36} - \frac{2(-2 + \sqrt{76})}{6} - 1

This gives us the y-coordinate of the first intersection point.

Similarly, substituting $x = \frac{-2 - \sqrt{76}}{6}$ into the function, we get:

y = 3 \left(\frac{-2 - \sqrt{76}}{6}\right)^2 - 2 \left(\frac{-2 - \sqrt{76}}{6}\right) - 1

Simplifying the equation, we get:

y = \frac{3(-2 - \sqrt{76})^2}{36} - \frac{2(-2 - \sqrt{76})}{6} - 1

This gives us the y-coordinate of the second intersection point.

Conclusion

In this article, we have used the functions $y = 3 x^2 - 2 x - 1$ and $y = 5 - 4 x$ to find the values of $a, b$ , and $c$ in the equation $ax^2 + bx + c = 0$ . We have found the intersections of the two functions and used these intersection points to find the values of $a, b$ , and $c$ . This approach provides a unique and interesting way to solve quadratic equations.

The Final Answer

The final answer is:

$a = 3$ $b = 2$ $c = -6$

References

[1] "Quadratic Equations" by Math Open Reference
[2] "Graphing Quadratic Functions" by Purplemath
[3] "Solving Quadratic Equations" by Khan Academy
Quadratic Equations: A Q&A Guide

In our previous article, we explored the equation $ax^2 + bx + c = 0$ and used the functions $y = 3 x^2 - 2 x - 1$ and $y = 5 - 4 x$ to find the values of $a, b$ , and $c$ . In this article, we will answer some frequently asked questions about quadratic equations.

Q: What is a quadratic equation?

A: A quadratic equation is a polynomial equation of degree two, which means the highest power of the variable (usually $x$ ) is two. The general form of a quadratic equation is $ax^2 + bx + c = 0$ , where $a$ , $b$ , and $c$ are constants.

Q: How do I solve a quadratic equation?

A: There are several methods to solve a quadratic equation, including factoring, completing the square, and using the quadratic formula. The quadratic formula is the most commonly used method and is given by:

x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Q: What is the quadratic formula?

A: The quadratic formula is a mathematical formula that gives the solutions to a quadratic equation. It is given by:

x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Q: How do I use the quadratic formula?

A: To use the quadratic formula, you need to plug in the values of $a$ , $b$ , and $c$ into the formula. The formula will then give you the solutions to the quadratic equation.

Q: What is the difference between a quadratic equation and a linear equation?

A: A quadratic equation is a polynomial equation of degree two, while a linear equation is a polynomial equation of degree one. In other words, a quadratic equation has a squared term, while a linear equation does not.

Q: Can I solve a quadratic equation by graphing?

A: Yes, you can solve a quadratic equation by graphing. By graphing the quadratic function, you can find the x-intercepts, which are the solutions to the quadratic equation.

Q: What is the significance of the discriminant in a quadratic equation?

A: The discriminant is the expression under the square root in the quadratic formula. It is given by $b^2 - 4ac$ . The discriminant determines the nature of the solutions to the quadratic equation. If the discriminant is positive, the equation has two real solutions. If the discriminant is zero, the equation has one real solution. If the discriminant is negative, the equation has no real solutions.

Q: Can I use a calculator to solve a quadratic equation?

A: Yes, you can use a calculator to solve a quadratic equation. Most calculators have a built-in quadratic formula function that you can use to solve the equation.

Q: What are some common mistakes to avoid when solving a quadratic equation?

A: Some common mistakes to avoid when solving a quadratic equation include:

Not simplifying the equation before solving it
Not using the correct formula or method
Not checking the solutions for validity
Not considering the nature of the solutions (real or complex)

Conclusion

In this article, we have answered some frequently asked questions about quadratic equations. We have covered topics such as the definition of a quadratic equation, methods for solving quadratic equations, and common mistakes to avoid. We hope that this article has been helpful in clarifying any doubts you may have had about quadratic equations.

The Final Answer

The final answer is:

A quadratic equation is a polynomial equation of degree two.
The quadratic formula is a mathematical formula that gives the solutions to a quadratic equation.
The discriminant determines the nature of the solutions to a quadratic equation.
You can use a calculator to solve a quadratic equation.
Some common mistakes to avoid when solving a quadratic equation include not simplifying the equation, not using the correct formula or method, not checking the solutions for validity, and not considering the nature of the solutions.

References

[1] "Quadratic Equations" by Math Open Reference
[2] "Graphing Quadratic Functions" by Purplemath
[3] "Solving Quadratic Equations" by Khan Academy