Question

a=15
d=10
Sn=2200
so find n and an

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Answer 1

Step-by-step explanation:

Answer :-

Given :-

First term (a) = 15

Common difference (d) = -3

Last term (an) = 0

To Find :-

Number of terms n

Solution :-

\huge{\boxed{\boxed{an \:=\: a \: +\:(n - 1)d}}}

an=a+(n−1)d

Putting values

» 0 = 15 + (n - 1)-3

» -15 = -3n + 3

» -15 - 3 = -3n

» -18 = -3n

» -18/-3 = n

» 6 = n

\huge{\boxed{\boxed{n \:=\:6}}}

n=6