.
Find the value of k and the 17-th term of each of the following arithmetic sequence
6) 2k+1,5k-3, 7k-2
7) 7k+2,5k+4,4k-5
~~~~~~~~~~~~~~~~~~~~~~~~~
I will solve first part, leaving the second part to you as an exercise,
because the second part is a TWIN to the first part.
Since three terms , and form an arithmetic progression,
the difference is the same as the difference
(as each this difference is simply d, the common difference of the AP).
So, we write
(5k-3) - (2k+1) = (7k-2) - (5k-3).
From this equation, we find the value of k
5k - 3 - 2k - 1 = 7k - 2 - 5k + 3,
3k - 4 = 2k +1
3k - 2k = 1 + 4
k = 5.
Now we know the value of k and can restore the values of the first three twrms of this AP
= 2*5+1 = 11;
= 5*5-3 = 22;
= 7*5-2 = 33.
Thus, the progression has first term 11 and the common difference d = 22-11 = 11.
At this point, we know everything about this AP and can easily find each of its terms.
In particular, the 17-th term of this AP is = + d*(n-1) = 11 + 11*(17-1) = 11 + 11*16 = 187. ANSWER
Solved.
This solution is your TEMPLATE to solve many other similar problems.
In particular, the other part is a TWIN and can be solved by the same way.
Literally follow my solution, step by step.
You may report me about your progress.