Do you understand the difference between a formula, expression, identity and equation?
A formula is a rule written using symbols that describe a relationship between different quantities. Typical maths formulae include
A = πr² (area of a circle)
C=πd (circumference of a circle)
An expression is a group of mathematical symbols representing a number or quantity. Expressions never have equality or inequality signs like =, >, <, ≠ ,≥ ,≤. Some examples
3xy + 4x
t² + t³
An identity is an equation that is always true, no matter what values are chosen.
3a + 2a = 5a
x²+x² = 2x²
5 x 10 = 10 x 5
An equation is a mathematical statement that shows that two expressions are equal. It always includes an equals sign.