SOLUTION: Find the 21st term of an arithmetic sequence whose first term is 9x and whose common difference is x + y.

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Question 1206399: Find the 21st term of an arithmetic sequence whose first term is 9x and whose common difference is x + y.
Answer by mananth(16946) About Me  (Show Source):
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Find the 21st term of an arithmetic sequence whose first term is 9x and whose common difference is x + y.
The nth term of an arithmetic sequence is
tn= a+(n-1) *d
a=first term =9x
d=common difference is x + y.
t(21)= 9x +(21-1)(x+y)
t(21) = 9x+20(x+y)
t(21) =9x+20x+20y
= 29x+20y