9514 1404 393
Answer:
Step-by-step explanation:
You know the general term of an AP is ...
an = a1 +d(n-1)
Here, a1 = k. The common difference is ...
2k/3 -k = -k/3
So, the general term is ...
an = k +(k/3)(n -1) . . . . the general term
__
The 6th term is then ...
a6 = k + (k/3)(6 -1) = (3k +5k)/3 = 8k/3 . . . . 6th term
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The 20th term is ...
a20 = k + (k/3)(20 -1) = 22k/3
If this is 15, then the value of k is ...
22k/3 = 15
22k = 45
k = 45/22 . . . . value of k for a20 = 15
