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Arithmetic progression formula an=a 1+(n- 1)d

The first n terms and formulas are: Sn=na 1+n(n- 1)d/2.

Sn=(a 1+an)n/2

If m+n=p+q, then: am+an=ap+aq exists.

If m+n=2p, then: am+an=2ap.

The general formula of (1) geometric series is: an = a 1× q (n- 1).

If the general formula is transformed into an = a 1/q * q n (n ∈ n *), when q > 0,

Then an can be regarded as a function of the independent variable n, and the point (n, an) is a set of isolated points on the curve y = a 1/q * q x.

(2) the relationship between any two am and an is an = am q (n-m).

(3) A1an = a2an-1= a3an-2 = … = akan-k+1,k ∈ {1 can be deduced from the definition of geometric series, the general term formula, the first n terms and the formula.

(4) Equal ratio mean term: AQAP = Ar 2, Ar is AP, and AQ is equal ratio mean term.

(5) Equal ratio summation: Sn = A 1+A2+A3+...+ Amp.

① when q≠ 1, sn = a1(1-q n)/(1-q) or sn = (a1-an× q) ÷ (/kloc)

If π n = A 1 A2 … an, then π2n- 1=(an)2n- 1, π 2n+1= (an+1) 2n+1.

I wish you progress in your study! I hope it helps you! ! ! !