It is given that 13, 17, 21, 25,... is an arithmetic sequence

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It is given that 13, 17, 21, 25,...  is an arithmetic sequence

Uniteasy Admin · Accepted Answer

$$17-13=4$$
$$21-17=4$$
So the series is an arithmetic sequence with common difference 4, $$a_1=13$$
The general term for the sequence is 
$$T_n=a_1+(n-1)d=13+4(n-1)$$
$$=4n+7$$ When $$n=10$$,
$$T_{10}=4	imes 10+7= 21$$

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