# Author's software

#### Being tested

The difference of arithmetic progression

Writing functions:

arphd(a, b, c, d)

Where:

a - n-th member of progression, b - m-th member of progression, c progression member n, d is the number of progression member m

The arphd function calculates the difference of the arithmetic progression. An arithmetic progression is a sequence of numbers in which each subsequent term is obtained by adding the same number to the previous one, called a difference. Often in mathematics and programming it is required to find this difference in order to solve various problems.

Our function takes 4 parameters: a progression element with number n (a), a progression element with number m (b), and the numbers of these members (c and d with numbers n and m). It returns a value that represents the difference in the arithmetic progression defined by these parameters.

In this way, the function performs the necessary calculations and returns the difference of the arithmetic progression based on the specified parameters.

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