Mathematics-Variable

A variable whose value may change within the set of operations. Variables are distinguished as dependent variable and independent variable. Independent variables are considered as input to a system and may take the different outputs depends upon the inputs. Dependent variables are those values that change when changes occured in the other values in the system.

In the below example.
y = x² + 5
y ---> Dependent Variable, its value changing when apply different value for x.
x ---> Independent Variable, it is considered as input to a system.

In the case of polynomial f(x) = ax² + bx + c
a, b, c are coefficients and considered as parameters, assumed to be fixed. But here x is a variable.

Naming coventions applied for some of the letters.

1 ) a_i is often used to denote term of sequence.
2) a, b, c, d are used to represent constants
3) f & g are commonly used for denoting functions
4) i, j, k are often used as subscripts.
5) m, n usually denote integers
6) p & q often denote prime numbers.
7) r for remainder
8) u & v used for denoting vertex
9) x, y, z corresponds to cartesian coordination axes
10)  z for complex number