Question

Determine whether the equation represents \(y\) as a function of \(x\). \(y^{2}=x^{2}-1\)

Short answer

The equation does not represent \(y\) as a function of \(x\), since for each \(x\) value, there can be two different \(y\) values.

Step-by-step solution

Rearrange the equation

First, the equation needs to be rearranged to get \(y\) by itself on one side. This can be done by taking the square root of both sides of the equation. The result is \(y=\sqrt{x^2-1}\) and \(y=-\sqrt{x^2-1}\) as the square root has plus or minus two values.

Analyze the resulting equation

Upon analysing the resulting equation, it is clear that for a given value of \(x\), there are two possible values for \(y\); one is positive and the other is negative. This violates the definition of a function, which should have a unique output value for each input value.

Key concepts

Function Definition

In algebra, understanding what a function is forms the bedrock upon which many other concepts are built. A function is essentially a special relationship between sets of numbers where each input, commonly referred to as the independent variable, is assigned exactly one output, known as the dependent variable. The most notable feature of a function is uniqueness; for every input there must be one and only one output.

This definition is crucial when working with equations to determine if they represent a function of a variable. As per the definition, if an equation yields more than one output for a single input, it cannot be classified as a function. This is precisely the issue we encounter in the exercise where the equation presented gives us two possible values of \(y\) for a single \(x\), indicating that \(y\) is not a function of \(x\) in this scenario.

Square Root

At the heart of many algebraic equations lies the square root, represented as \(\sqrt{x}\), which is defined as a value that, when multiplied by itself, gives the original number \(x\). For instance, the square root of 9 is 3, since \(3 \times 3\) equals 9. However, square roots can be tricky due to their dual nature; every positive number actually has two square roots: a positive and a negative one.

When dealing with square roots in algebra, we encounter the concept of 'principal square root', usually meaning the positive square root. Nonetheless, in the context of functions, one must consider both the positive and negative square roots to avoid overlooking any potential solutions. This is evident in the exercise where both \(\sqrt{x^2-1}\) and \(-\sqrt{x^2-1}\) are considered for the value of \(y\).

Algebraic Manipulation

Algebraic manipulation involves rearranging, simplifying or transforming algebraic expressions using a variety of methods including factoring, expanding, and using inverse operations. These techniques enable us to solve for variables, compare different expressions, and determine the characteristics of equations like whether they represent functions or not.

In our exercise, algebraic manipulation was employed in the form of taking a square root to isolate \(y\) from the equation \(y^2 = x^2 - 1\). The manipulation, while simple, demonstrates a key step in solving algebra-related problems. By isolating \(y\), we could further analyze the nature of the relationship between \(y\) and \(x\). This process, while indispensable for solving equations, also unfolds the complexity of roots in an equation, leading us back to the issue of functions and their unique outputs.