SOLUTION: the end term of the sequence is 9x-z. the third term is 25 so what is the value of z? (the description is (a+n-1d) )

Algebra ->  Sequences-and-series -> SOLUTION: the end term of the sequence is 9x-z. the third term is 25 so what is the value of z? (the description is (a+n-1d) )      Log On


   

Question 1011296: the end term of the sequence is 9x-z. the third term is 25 so what is the value of z? (the description is (a+n-1d) )
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
n is for the index of a term.
First term is a%5B1%5D%2B%281-1%29%2Ad=a%5B1%5D%2B0%2Ad=a%5B1%5D.
Term at n=3 is a%5B1%5D%2B%283-1%29%2Ad=a%5B1%5D%2B2d.
The index for your last term of the sequence is unknown n, so it is a%5B1%5D%2B%28n-1%29d, and is given as the expression;
highlight_green%289x-z=a%5B1%5D%2B%28n-1%29d%29, and you do not know x, a%5B1%5D, n, d.

You want to find the value for z, yet the other needed quantities for x, a%5B1%5D, n, and d are still unknown.

The term for index of 3 is a%5B1%5D%2B2d=25. You can use this to find a formula for either a%5B1%5D OR for d. You will still have three unknown, undetermined variables. Do you understand the difficulty here?

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