 learn about expression, equation, and formulas. What is an expression? An expression is a combination of numbers, operators, brackets, and a variable. What do we mean? A times B, we have variables, an operation multiplication, and another variable B. A squared plus B squared, it's also a combination. Of variables, operators, which is the addition. So a variable A and a variable B. And also two multiplied by four Y plus six into bracket. It's also a combination of numbers, brackets, brackets, variables, and operations. When we have an expression, we can then create an equation. An equation is when we take an expression and put an equal sign to it. For example, we can convert A multiplied by B into A equation by saying A multiplied by B. A multiplied by B is equals to zero. By putting an equal sign, we made that expression an equal sign. Another example of an equation is two X plus three is equals to nine. Sometimes an equation can become what we call a formula. And a formula is an expression which represents a relationship between different variables. For example, if I want to know what is the relationship between X and Y, we use the formula Y is equals to AX plus B which gives you the equation of a straight line. But in a way, it tells you the relationship between your X values and your Y values. The other type of a formula is a formula for a circle, the area of a circle. Thank you for listening.