Question

Represent the solution graphically. Check the solution algebraically. $$ 8 x^{2}-4=4 x $$

Short answer

The roots of the quadratic function, derived from the algebraic solution, serve as the x-intercepts when the function is graphed. Upon substituting these roots back into the original equation, if they satisfy the equation, the solution has been correctly obtained and checked.

Step-by-step solution

Rewrite the equation to standard form

By subtracting \(4x\) from both sides, we have:\(8x^2 - 4x - 4 = 0\)

Solve the quadratic equation

The roots of the quadratic can be found using the quadratic formula:\(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\)Substituting \(a = 8\), \(b = -4\), and \(c = -4\) into the formula, the roots, \(x_1\) and \(x_2\), can be found.

Check the solution algebraically

Substitute the solutions back into the original equation to verify that both are correct. If both solutions satisfy the original equation, then they are the correct solutions.

Represent the solution graphically

Plot the quadratic function, \(y = 8x^2 - 4x - 4\). The roots obtained in Step 2, represented by the points \((x_1, 0)\) and \((x_2, 0)\) on the graph, are the x-intercepts of the function.

Key concepts

Quadratic Formula

The quadratic formula is a powerful tool used to find the roots of a quadratic equation. It is written as: \[\begin{equation}x = \frac{{-b \/pm \sqrt{{b^2 - 4ac}}}}{{2a}}\end{equation}\]where a, b, and c are coefficients of the quadratic equation in its standard form ax^2 + bx + c = 0. The solutions, or roots, are the values of x for which the quadratic equation equals zero. These solutions can be real or complex numbers depending on the discriminant \Delta = b^2 - 4ac. If the discriminant is positive, we get two distinct real roots; if it is zero, there is one real root; and if negative, the roots are complex.

Using the quadratic formula provides a systematic way to solve any quadratic equation, even if factoring or other methods are not suitable. It's essential for students to understand this formula because it can be used to tackle an extensive variety of problems.

Graphical Representation of Solutions

The graphical representation of the solutions to a quadratic equation involves the plotting of a parabola on the coordinate plane. The standard form of a quadratic function is y = ax^2 + bx + c. The parabola either opens upwards or downwards depending on the sign of the coefficient a. The points where the parabola crosses the x-axis, (the x-intercepts), represent the solutions of the quadratic equation.

To graph our quadratic function, we first need to identify the vertex, axis of symmetry, and the y-intercept. After plotting these key points and the x-intercepts found using the quadratic formula, we can sketch the parabola. The graphical representation is not just a visualization. It lends insight into the behavior of the quadratic function, the maximum and minimum values it can achieve (vertex), and the direction in which it opens.

Standard Form of Quadratic Equations

A quadratic equation is often expressed in its standard form, which is ax^2 + bx + c = 0. Here, a, b, and c are constants with a not equal to zero. This form is very convenient as it directly reveals the coefficients used in the quadratic formula.

In the given exercise, rewriting the quadratic equation into the standard form simplified the problem. Organizing an equation into this form also aids in recognizing the parabola's direction of opening, as positive a means the parabola opens upward, while negative a will be opening downward. Even if students are using technology to solve the quadratic equations, understanding how to express them in standard form is crucial for interpreting the results and verifying solutions.

Algebraic Verification of Solutions

After calculating the roots of a quadratic equation, it is essential to ensure that these solutions are accurate. We do this through algebraic verification, which means substituting the solutions back into the original equation. If the original equation balances, meaning the left and right sides are equal, then the solutions are correct. This is the ultimate check of the problem-solving process.

For example, given the roots from the quadratic formula, we would replace x in the original equation 8x^2 - 4x - 4 = 0 with each root. If both sides equate to zero with the roots, we've confirmed the correctness of our solutions. This step is crucial because it verifies that our solutions not only satisfy the standard form but are indeed the solutions for the specific quadratic equation we are tasked with solving.