Sequences and Series Arithmetic Progression What is AP ? When the sequences or series number increase or decreases by the fixed quantity , then the sequence or series is known Arithmetic progression. General Expression of A.P. : a , a+d , a + 2d , a+3d ......... where a is the first term and d is common difference nth term (a n ) : It represent the nth term of an A.P. , and it can be write down as a n = a + (n-1)d NOTE : The difference between consecutive terms is always d Sum of first n terms of an A.P. S n = a + (a+d) + (a+2d) + ....... + (a + (n-1)d) Arithmetic Mean (AM) : When three numbers are in A.P. , then middle one is called arithmetic mean of other two. If a and b are two number and AM is the arithmetic mean of a and b , it means a , AM , b are in A.P. How to insert n arithmetic means between two numbers AM 1 , AM 2 , AM 3 .....AM n are n arithmetic means between two numbers a and b , So the seque...