Question

in an ap s21=12500 s20=1200 find a21​

Answer 1

we know that an=sn-s (n-1)

so a21=s21-s20

a21=12500-1200

a21=11300

Answer 2

given:

s21=12500

s20=1200

to prove:

a21=?

prove:

a21=s21-s20

a21=12500-1200

a21=11300

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