SOLUTION: Find the valee of k and the 17 term of each of the following arithmetic sequence 6)2k+1,5k-3, 7k-2 7) 7k+2,5k+4,4k-5

Algebra ->  Sequences-and-series -> SOLUTION: Find the valee of k and the 17 term of each of the following arithmetic sequence 6)2k+1,5k-3, 7k-2 7) 7k+2,5k+4,4k-5      Log On


   



Question 1208027: Find the valee of k and the 17 term of each of the following arithmetic sequence
6)2k+1,5k-3, 7k-2
7) 7k+2,5k+4,4k-5

Found 2 solutions by mccravyedwin, ikleyn:
Answer by mccravyedwin(407) About Me  (Show Source):
You can put this solution on YOUR website!



The last two equations give us the system

system%285k-3=%282k%2B1%29%2Bd%2C7k-2=%285k-3%29%2Bd%29

Simplify those equations and solve the system by substitution
or elimination.  You will then have the values for k and d. Then
find a1 by substituting the value for k in a%5B1%5D=2k%2B1.

Then write out the first 17 terms beginning with a1 and 
add d over and over until you have 17 terms.

Oh, maybe by "17 term" you meant the "17th term" and not the "17 terms".

If so, use a%5Bn%5D=a%5B1%5D%2B%28n-1%29d with n=17. 

Do the other one the same way.

Edwin
 

Answer by ikleyn(52790) About Me  (Show Source):
You can put this solution on YOUR website!
.
Find the highlight%28cross%28valee%29%29 value of k and the highlight%28cross%2817%29%29 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 a%5B1%5D,  a%5B2%5D and a%5B3%5D form an arithmetic progression,
the difference  a%5B2%5D-a%5B1%5D is the same as the difference  a%5B3%5D-a%5B2%5D
(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

    a%5B1%5D = 2*5+1 = 11;

    a%5B2%5D = 5*5-3 = 22;

    a%5B3%5D = 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  a%5B17%5D = a%5B1%5D + 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.