how to solve arithmetic sequence (find the N) with quadratic equation

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how to solve arithmetic sequence (find the N) with quadratic equation



A= 75 (price per floor) D=3.70(price increase per floor) N=? (what floor that cost $$2820.50 within a couple of Dollar)
and the value of N has to meet the $2820.50 (within a couple of Dollar)



Answer that i have right now



$$SN=x(2xa+(n-1)xd)$$



$$=24÷2x(2x75+(24-1)x3.70)$$



$$=$ 2821.2$$
Now the way that i found the answer of N (24 Floors) is by using trial and error to meet the value, the problem is my teacher want me to solved the N term with quadratic equation



Question
how do i know the N term is 24 (floors) with quadratic equation?



Thanks You guys :)




sequences-and-series geometry quadratics




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    up vote
    -1
    down vote

    favorite












    how to solve arithmetic sequence (find the N) with quadratic equation



    A= 75 (price per floor) D=3.70(price increase per floor) N=? (what floor that cost $$2820.50 within a couple of Dollar)
    and the value of N has to meet the $2820.50 (within a couple of Dollar)



    Answer that i have right now



    $$SN=x(2xa+(n-1)xd)$$



    $$=24÷2x(2x75+(24-1)x3.70)$$



    $$=$ 2821.2$$
    Now the way that i found the answer of N (24 Floors) is by using trial and error to meet the value, the problem is my teacher want me to solved the N term with quadratic equation



    Question
    how do i know the N term is 24 (floors) with quadratic equation?



    Thanks You guys :)




    sequences-and-series geometry quadratics




    share|cite|improve this question























      up vote
      -1
      down vote

      favorite









      up vote
      -1
      down vote

      favorite











      how to solve arithmetic sequence (find the N) with quadratic equation



      A= 75 (price per floor) D=3.70(price increase per floor) N=? (what floor that cost $$2820.50 within a couple of Dollar)
      and the value of N has to meet the $2820.50 (within a couple of Dollar)



      Answer that i have right now



      $$SN=x(2xa+(n-1)xd)$$



      $$=24÷2x(2x75+(24-1)x3.70)$$



      $$=$ 2821.2$$
      Now the way that i found the answer of N (24 Floors) is by using trial and error to meet the value, the problem is my teacher want me to solved the N term with quadratic equation



      Question
      how do i know the N term is 24 (floors) with quadratic equation?



      Thanks You guys :)




      sequences-and-series geometry quadratics




      share|cite|improve this question













      how to solve arithmetic sequence (find the N) with quadratic equation



      A= 75 (price per floor) D=3.70(price increase per floor) N=? (what floor that cost $$2820.50 within a couple of Dollar)
      and the value of N has to meet the $2820.50 (within a couple of Dollar)



      Answer that i have right now



      $$SN=x(2xa+(n-1)xd)$$



      $$=24÷2x(2x75+(24-1)x3.70)$$



      $$=$ 2821.2$$
      Now the way that i found the answer of N (24 Floors) is by using trial and error to meet the value, the problem is my teacher want me to solved the N term with quadratic equation



      Question
      how do i know the N term is 24 (floors) with quadratic equation?



      Thanks You guys :)





      sequences-and-series geometry quadratics





      share|cite|improve this question












      share|cite|improve this question




      share|cite|improve this question








      edited Jul 26 at 8:54
























      asked Jul 26 at 8:36









      charless

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