Solve the following:
1. Find the general term of an arithmetic sequence whose 9th term is 26 and
20th term is 59.
2. Find the first term of an arithmetic sequence whose 41st term is -124 and
the common difference is -3.
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Solve the following:
1. Find the general term of an arithmetic sequence whose 9th term is 26 and
20th term is 59.
2. Find the first term of an arithmetic sequence whose 41st term is -124 and
the common difference is -3.
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Answer:
1.an=3n-1
2. -4
Step-by-step explanation:
1. Since the 9th and 20th term of the sequence are given. the common difference of it would be 3.
an=3n-1 an=3n-1
an=3(9)-1 an=3(20)-1
an=27-1 an=60-1
an=26 an=59
thus the sequence must be like this:
2,5,8,11,14,17,20,23,26(9th term),29,32,35,38,41,44,47,50,53,56,59(20th term)
2. Given: an=-124, d=-3, n=41
an=a1+(n-1)d
-124=a1+(41-1)(-3)
-124=a1+(40)(-3)
-124=a1+(-120)
-124+120=a1
-4=a1