Problem 26 - Algebra 1

Question

Solve the equation algebraically. Check the solutions graphically. $$ \frac{1}{2} x^{2}=18 $$

Step-by-Step Solution

Answer

The solutions to the equation \(\frac{1}{2} x^{2} = 18\) are \(x = 6\) and \(x = -6\).

Step 1: Isolate \(x^2\)

Multiply both sides by 2 to get rid of the fraction on the left hand side. This results in the equation \(x^{2} = 36\).

Step 2: Square root both sides

In order to solve for \(x\), one must square root both sides of the equation. It is important to remember that when we square root both sides of equation, there are two solutions, one positive and one negative. This results in the equations \(x = ± √36\).

Step 3: Calculate the values of x

The square root of 36 is 6. Thus, the solutions of the equation after square rooting both sides are \(x = 6\) and \(x = -6\).

Step 4: Graphical representation of solutions

Plot these points on a graph of the function \(\frac{1}{2} x^{2}\). This is best done graphing \(y= \frac{1}{2} x^{2}\), and checking where y=18 intersects the function. The points of intersection correspond with the solutions to the equation.

Key Concepts

Algebraic Solutions

When solving quadratic equations, the algebraic approach is a fundamental method. In this exercise, we begin with the equation \(\frac{1}{2} x^{2} = 18\). To solve it, our first step is to eliminate the fraction by multiplying both sides by 2, which simplifies the equation to \(x^{2} = 36\).
This is a crucial step because it isolates the variable \(x\) and makes the equation easier to handle. It demonstrates the importance of performing equal operations on both sides of an equation to maintain balance.

Once the quadratic equation is simplified to \(x^{2} = 36\), we proceed to the next part: solving for \(x\). This involves using mathematical operations to isolate \(x\) and find its possible values. For quadratic equations like this, the square root method becomes particularly handy. Note that algebraic solutions often aim to find all possible values of \(x\) that satisfy the original equation.

Graphical Representation of Solutions

Understanding solutions graphically is vital to reinforce the algebraic results we derive. A function's graph can often give us visual insights into the solutions. Here, our function is \(y = \frac{1}{2} x^{2}\), and we compare it to a constant line \(y = 18\).

By plotting both the parabola and the horizontal line on a graph, we can visually locate the points where they intersect. These intersection points correspond to the solutions of our original equation \(\frac{1}{2} x^{2} = 18\).

The graph provides two intersection points: where \(x\) equals 6 and -6. These align perfectly with our algebraic solutions. This graphical representation not only confirms our calculated solutions but also illustrates the symmetric nature of quadratic functions around the origin point on the graph.

Square Root Method

The square root method is a straightforward technique used to solve quadratic equations, especially when these equations are in the form \(x^{2} = c\), where \(c\) is a constant. In this example, with the equation \(x^{2} = 36\), we apply the square root method by taking the square root of both sides.

It is essential to remember that when taking the square root of both sides, we consider both the positive and negative square roots. Hence, this method highlights an important concept: quadratics can have more than one solution. For \(\sqrt{36}\), the results are \(x = 6\) and \(x = -6\).

This method is particularly effective for equations that are perfect squares. It showcases the elegant simplicity of algebraic manipulation in finding solutions, and it's a vital tool in any student's math skillset.