Working with formulas > Using formulas
1234Using formulas


A formula is a sentence containing variables. Formulas often describe a relation between those variables, but not always.
Formulas often look like an equation, i.e. a sentence with an equals sign.
If a formula describes a relation between two variables, you can draw a corresponding graph. First, you make a table. Next you draw the points in a coordinate system and connect them.

In practice, formulas often describe relationships between quantities. Those quantities are represented by a variable, a letter which corresponds to the name of the quantitiy used.
A quantity is measured in units.

  • The formula A = z 2 is an equation defining the relation between the variables A and z . You can make the corresponding table and plot the corresponding graph.

  • The formula 2 t + 40 = 300 gives information about the unknown t . The solution to this equation is t = 130 , for 2 130 + 40 = 300 .

  • The formula ( x + 3 ) 2 = x 2 + 6 x + 9 is a calculation rule and is valid for all x .

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