Contrarily to Viète's convention, Descartes' is still commonly in use. In 1637, René Descartes 'invented the convention of representing unknowns in equations by x, y, and z, and knowns by a, b, and c'. François Viète's convention was to use consonants for known values and vowels for unknowns. How much more time pass, the distance you traveled increase in a same speed.įrançois Viète introduced at the end of 16th century the idea of representing known and unknown numbers by letters, nowadays called variables, and of computing with them as if they were numbers, in order to obtain, at the end, the result by a simple replacement. The speed is a exemple: if you have a constant speed, then the distance is the dependent variable and the time is the independent variable.

In a function, for exemple, we have two variables: one is independent and other is dependent for the first one which means that when you change intentionally the independent then the dependent changes too. Thats why we use them: to work when we dont know the answer yet. Now, you have 2 variables and several responses.

I have a statement and x is a variable because it can be any real number, but in truth it is a question: what numbers i can put in place the x and the results will be true? The answer how you know is 2. Therefore, a variable works how a question. But, if you put a variable in a statement, so the proposition can be false and true either for different values. In Math, when you make a statement, then it can be false or true. Now, a variable can be anything, it depends of the statement. For exemple: give a tip for a good waiter. In this case, tips are the sum of money given to someone as a reward for a service.

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