Arithmethic sequence

centii

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Mar 25, 2020
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Q1. Find the 18th term of this arithmetic sequence 15, 11, 7,

Q2. Find the 30th term of this arithmetic sequence 1/2, 1, 3/2, ...
 
Q1. Find the 18th term of this arithmetic sequence 15, 11, 7,
Q2. Find the 30th term of this arithmetic sequence 1/2, 1, 3/2, ...
You need to find the common difference,\(~d\). If the given sequence is \(a_1,~a_2,~a_3\)
then \(d=a_3-a_2=a_2-a_1\). Now write \(a_n=a_1+(n-1)\cdot d\) as the \(n^{th}\) term.
Please post your work.
 
Q1. Find the 18th term of this arithmetic sequence 15, 11, 7,

Q2. Find the 30th term of this arithmetic sequence 1/2, 1, 3/2, ...
pka gave you the formula for an which is the nth term. To use it, you need the first term which is a1 in the formula and the change from one term to the next which is d.
You find d by subtracting: any term minus the one before it.
 
For Q.1, common difference is 4. i,e. d=4; first term is a= 15 & n= 18
Simply put the values in following formula to get the answer-
an=a+(n−1)d
I think similarly, you can find answer for Q.2
 
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