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last term an = a+(n-1)d

sum to n terms = n/2 (2a+(n-1)d) or

= n/2(a+l)

common ratio r = a₂/a₁

geometric progression:-

last term = a(r) power n-1

sum to n terms = a(r power n-1/r-1) r>1

ar r=1

a (1-r power n/ 1-r) r<1

Arithmetic progression:-

tn=a+(n-10)d

n=a+b÷2

Sn=n÷2(2a+n-1×d)or

Sn=n÷2(a+l)

tn=a+(n-10)d

n=a+b÷2

Sn=n÷2(2a+n-1×d)or

Sn=n÷2(a+l)