Question

arthamatic progressions of a ap where and how do we now the formulla to use their

Answer 1

arithmetic progression has only four formulas.
An= a+( n - 1)d
Sn= n/2 ( 2a + ( n-1) d)
Sn= n/2 ( a + l).
the last formula remains changing according to the term you have to find.
this is like...
a+d=a2
a+ 2d= a3 and so on.
the values are
a is the first term of AP.
d is the equal difference between terms.
Sn is the sum of n terms.
n is no. of terms.

Answer 2

An=a+(n-1)d Sn=n/2(2a+(n-1)d Sn=n/2(a+1)