Constant is a value, that can’t change. For example, if we put x=2 then x will be a constant with value 2.
Variable is a value that may change within the scope of set. For example, if x is a natural number and variable, then x can be equal to 1 or 2 or some else natural number.
Constants are usually known and variables unknown. For example, we have to solve an equation: 2x+4=0
Here, x is a variable, that can be equal to any real number. We have to find such real value, satisfied the equation. This value is equal to -2, hence x=-2.
We can rewrite our equation in form& ax+b=0
where a, b are constants which equal to 2 and 4 respectively.
As u can see, a and b are known and x is unknown and we have to find it.
Variables are further distinguished as being either a dependent variable or an independent variable. Independent variables are regarded as inputs to a system and may take on different values freely. Dependent variables are those values that change as a consequence of changes in other values in the system. For example, if we have two variables x and y, which are both real numbers, then we can call one of them (for example x) independent variable and other dependent.
To do this we have to make a correspondence between x and y. Let& y=x+3
If we know x, then we can also calculate y, by adding 3 to x.
Some more examples:
2, 15, -5, ½ are all constants.
x (as a real number), n (as a natural number), r(some rational number) are all variables.
x=2y+3z y and z are independent real numbers, x is dependent real number.