the 5th term of an arithmetic sequence is 38 and 9th term is 66 what is it's 30th term what is it's first term and write the common difference
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25th term is equal to 178.
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Given :-
5 th term of an arithmetic sequence is 38 and 9th term is 66
To Find :-
What is it's 30th term what is it's first term and write the common difference
Solution :-
We know that
nth term = a + (n - 1)d
For 5th term
38 = a + (5 - 1)d
38 = a + 4d (1)
For 9th term
66 = a + (9 - 1)d
66 = a + 8d (2)
Subtracting both
a + 8d - a - 4d = 66 - 38
8d - 4d = 28
4d = 28
d = 28/4
d = 7
From 1
38 = a + 4(7)
38 = a + 28
38 - 28 = a
10 = a
i) 30th term
a_{30} = a + (n - 1)d
a_{30} = 10 + (30 - 1)7
a_{30} = 10 + 29(7)
a_{30} = 10 + 203
a_{30} = 213
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