## Arithmetic progression:

### Progression's elements:

a_{1},
a_{2},
a_{3}, ... ,
a_{n}

### Progression's denominator:

d

### Progression's element calculation formulas:

### Progression's n-th element calculation formula:

a_{n} =
a_{1} +
(n − 1) d

### Sum of the first n-elements of progression formulas:

## Geometric progression:

### Progression's elements:

b_{1},
b_{2},
b_{3}, ... ,
b_{n}

### Progression's denominator:

q, if
| q | < 1,
then progression is called infinitely decreasing progression

### Progression's element calculation formulas:

### Progression's n-th element calculation formula:

### Sum of the first n-elements of progression formula:

### Sum of the infinitely decreasing progression's formula: