$$(x1,y1) = "First Point Value"$$
$$(x2,y2) = "Secondo Point Value"$$

Equation Definition

It is an equality which has at least one unknown value that must be cleared,
these unknowns values are represented by letters.

Formula Definition

It is a representation of a rule or a general principle using letters. (Algebra, A. Baldor)
When describing formulas in plural, it is also valid to say "formulae".

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