Equations and Identities

Equations and Identities

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Understanding the Different Mathematical Terminologies

When studying mathematics, you may encounter various equations, identities, expressions, and formulae. It's essential to understand the differences between these terms to excel in GCSE math. Let's delve into each one in detail.


To better understand expressions, we first need to break down the components. An expression comprises of mathematical terms linked by operations. A mathematical term is a single number or letter with a coefficient, like 3x2 or x. Some examples of expressions include x + 5, 2y - 7, and 3x2.


As the name suggests, an equation is a statement that shows the equality of two expressions. It is represented by an equal sign, also known as the equality symbol. For instance:

  • x + 5 = 10
  • 2y - 7 = 3

An equation is only true under specific conditions, and the value of the variables must be known for the equation to hold true.


Some expressions are always equal, regardless of the values of the variables. These are known as identities and are represented by the identity symbol, which resembles an equal sign with an extra line. For example:

  • x + 5 ≡ x + 5
  • 2y - 7 ≡ 2y - 7

An identity is always true and is not limited to specific conditions, unlike an equation.

The Difference Between Equations and Identities

The main difference between equations and identities is that equations are only equal for a specific value, while identities are always equal. In other words, an equation has a specific solution, while an identity does not.

Furthermore, solving for the variables in an equation is necessary to determine its solution, while an identity does not have a specific solution.


A formula is a specialized equation that represents a general rule or fact that can be applied in different scenarios. For example, the quadratic formula is a well-known formula in GCSE mathematics.

It's important to note that formula is the singular form, while formulae is the plural form. It's crucial to understand that formulae are not to be confused with equations or identities, as they serve a different purpose.

With a better understanding of expressions, equations, identities, and formulae, you'll be better equipped to tackle various mathematical problems in your GCSE exam. Keep practicing and keep learning!

Understanding the Differences: Equations, Identities, Expressions, and Formulas

In mathematics, we often encounter various terms such as equations, identities, expressions, and formulas. These terms may seem similar, but they have distinct differences. Let's delve into their definitions and see how they are related and yet different from one another.

An equation is a mathematical statement written with an equal sign, where two expressions are related to one another. This means that the equation is true only for specific values of the expressions, and not for all values.

On the other hand, an identity is an equation where the two expressions are always equal, regardless of the values you substitute in. In other words, an identity holds true for all possible values. Hence, we can say that identities are a special type of equation.

Now, let's look at what expressions, equations, identities, and formulas are in simpler terms. An expression is a group of mathematical terms connected by operations. An equation is when two expressions are equal for specific values, while an identity is when two expressions are always equal, regardless of the values. Lastly, a formula is a set of instructions or rules that help us solve a specific problem or find a particular result. It acts as a guide for solving mathematical problems.

To better understand these terms, let's consider some examples. The formula for the area of a circle, A = πr2, is a formula as it helps us calculate the area when given the radius. An expression would be something like 2x + 3y, where the terms are connected by mathematical operations. The equation 2x + 3y = 10 is only true for specific values of x and y, making it an equation, not an identity. On the other hand, the identity 2x + 3y = 2x + 3y is true for all values of x and y, represented by the identity symbol ≡.

Applying the Concepts

Now, let's solve a problem that requires us to work with an identity.

For the identity 4x + 5y = 4x + 5y, find the values of x and y.


We know that the left side must be equal to the right side since it is an identity. The coefficient of x on the right side is 4, so it must also be 4 on the left side. Similarly, the coefficient of y on the right side is 5, so it must also be 5 on the left side. Thus, x = 4 and y = 5. We can also rearrange the equation to get 4(x + y) = 4(x + y). Since both sides have the same coefficient of (x + y), we can say that 4 = 4. It may seem redundant, but this step confirms that the values we found for x and y are indeed the only solutions for this identity.

In Conclusion

In summary, understanding the nuances between equations, identities, expressions, and formulas is crucial for success in mathematics. Remember, an equation is a general term for any mathematical relation with an equality sign, while an identity is a specific type of equation where the expressions are always true. With practice and a clear grasp of these concepts, you'll be able to handle any math problem with ease!

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