Question

Find the 25th term of the AP: 21,18,15,.....?

Answer 1

here the first term ,a=21
and d=18-21=-3
thus a25=a+(25-1)d
a25=21+24*-3
=21-72
=-51
thus the 25th term of this series is -51

Answer 2

a =21
d=18-21=-3
n=25
an=a+(n-1)d
=21+(25-1)-3
=21-72
=-51
hope it helps
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