Alternating Series: Intervals











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can you take a look at the link below where I uploaded a math problem solved by my professor. In part d), how did he arrive to -0.234? The -0.242 is 0.008 + that 0.234, but both intervals are negative. Both interval numbers have confused me, I'd appreciate it if someone could clarify. I would ask him but it's the weekend and I need to understand before I proceed with the problem.



Thank you!



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    up vote
    1
    down vote

    favorite












    can you take a look at the link below where I uploaded a math problem solved by my professor. In part d), how did he arrive to -0.234? The -0.242 is 0.008 + that 0.234, but both intervals are negative. Both interval numbers have confused me, I'd appreciate it if someone could clarify. I would ask him but it's the weekend and I need to understand before I proceed with the problem.



    Thank you!



    enter image description here










    share|cite|improve this question


























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      can you take a look at the link below where I uploaded a math problem solved by my professor. In part d), how did he arrive to -0.234? The -0.242 is 0.008 + that 0.234, but both intervals are negative. Both interval numbers have confused me, I'd appreciate it if someone could clarify. I would ask him but it's the weekend and I need to understand before I proceed with the problem.



      Thank you!



      enter image description here










      share|cite|improve this question















      can you take a look at the link below where I uploaded a math problem solved by my professor. In part d), how did he arrive to -0.234? The -0.242 is 0.008 + that 0.234, but both intervals are negative. Both interval numbers have confused me, I'd appreciate it if someone could clarify. I would ask him but it's the weekend and I need to understand before I proceed with the problem.



      Thank you!



      enter image description here







      calculus






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      edited Nov 17 at 16:19









      José Carlos Santos

      142k20112208




      142k20112208










      asked Nov 17 at 16:13









      RochNoure

      134




      134






















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          We are evaluating the sum up to the first 10 terms and we obtain $-0.2346$ since the next term is negative we are over estimating the sum and the lower bound is obtained adding the $11^{th}$ term which leads to $-0.2421$.



          The key fact is that the upper sum (even terms) is decreasing and the lower sum (odd terms) is increasing that is for any $n$



          $$S_{2}le S_{4} le ldots le S_{2n}le S_{infty} le S_{2n-1} le ldots le S_{3}le S_{1}$$






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          • Got it. Thank you both!!
            – RochNoure
            Nov 17 at 16:55











          Your Answer





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          1 Answer
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          1 Answer
          1






          active

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          active

          oldest

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          active

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          up vote
          1
          down vote



          accepted










          We are evaluating the sum up to the first 10 terms and we obtain $-0.2346$ since the next term is negative we are over estimating the sum and the lower bound is obtained adding the $11^{th}$ term which leads to $-0.2421$.



          The key fact is that the upper sum (even terms) is decreasing and the lower sum (odd terms) is increasing that is for any $n$



          $$S_{2}le S_{4} le ldots le S_{2n}le S_{infty} le S_{2n-1} le ldots le S_{3}le S_{1}$$






          share|cite|improve this answer























          • Got it. Thank you both!!
            – RochNoure
            Nov 17 at 16:55















          up vote
          1
          down vote



          accepted










          We are evaluating the sum up to the first 10 terms and we obtain $-0.2346$ since the next term is negative we are over estimating the sum and the lower bound is obtained adding the $11^{th}$ term which leads to $-0.2421$.



          The key fact is that the upper sum (even terms) is decreasing and the lower sum (odd terms) is increasing that is for any $n$



          $$S_{2}le S_{4} le ldots le S_{2n}le S_{infty} le S_{2n-1} le ldots le S_{3}le S_{1}$$






          share|cite|improve this answer























          • Got it. Thank you both!!
            – RochNoure
            Nov 17 at 16:55













          up vote
          1
          down vote



          accepted







          up vote
          1
          down vote



          accepted






          We are evaluating the sum up to the first 10 terms and we obtain $-0.2346$ since the next term is negative we are over estimating the sum and the lower bound is obtained adding the $11^{th}$ term which leads to $-0.2421$.



          The key fact is that the upper sum (even terms) is decreasing and the lower sum (odd terms) is increasing that is for any $n$



          $$S_{2}le S_{4} le ldots le S_{2n}le S_{infty} le S_{2n-1} le ldots le S_{3}le S_{1}$$






          share|cite|improve this answer














          We are evaluating the sum up to the first 10 terms and we obtain $-0.2346$ since the next term is negative we are over estimating the sum and the lower bound is obtained adding the $11^{th}$ term which leads to $-0.2421$.



          The key fact is that the upper sum (even terms) is decreasing and the lower sum (odd terms) is increasing that is for any $n$



          $$S_{2}le S_{4} le ldots le S_{2n}le S_{infty} le S_{2n-1} le ldots le S_{3}le S_{1}$$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Nov 17 at 16:44

























          answered Nov 17 at 16:26









          gimusi

          88.7k74394




          88.7k74394












          • Got it. Thank you both!!
            – RochNoure
            Nov 17 at 16:55


















          • Got it. Thank you both!!
            – RochNoure
            Nov 17 at 16:55
















          Got it. Thank you both!!
          – RochNoure
          Nov 17 at 16:55




          Got it. Thank you both!!
          – RochNoure
          Nov 17 at 16:55


















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