Solve for n: 2n² - 4n + 7 = 34, n > 1 | Example and Explanation

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The discussion revolves around solving the equation an = 2n² - 4n + 7 for n > 1 and verifying calculations. Participants clarify the computation of a4, with one asserting that the correct value is 23 rather than 9. There is confusion regarding the sum of elements, with a total of 48 being questioned. Additionally, the equivalence class problem is discussed, comparing it to a similar example in a textbook. The conversation emphasizes the importance of accuracy in calculations and understanding equivalence classes.
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Code: 
a[sub]n[/sub] = 2n[sup]2[/sup] - 4n + 7 
n>1
  -
4
Ea[sub]i[/sub] 5+7+13+9=34
i=1

a[sub]4[/sub] = 2(4)[sup]2[/sup] - 4(4) + 7 = 32 - 23 = 9
34?
 
Last edited:
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Check your a4.. 7 is added, not substracted.
 
Code: 
How about this
a[sub]n[/sub] = 2n[sup]2[/sup] - 4n + 7 
n>1
  -
4
Ea[sub]i[/sub] 5+7+13+23=48
i=1

a[sub]4[/sub] = 2(4)[sup]2[/sup] - 4(4) + 7 = 32 - 16 + 7 = 23
48?
 
How about this one;
Y={2,5} C={1,2}
List the elements of [C], the equivalence class containg C
{1}{2}{1,5}{1,2,5}

The example in my book is the same question but Y={3,4} and C={1,3}
and the solution is {1}{1,3}{1,4}{1,3,4}
 
Is 48 correct for the first one?
 

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