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

[ptex]

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?

 

[pig]

Check your a4.. 7 is added, not substracted.

 

[ptex]

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?

 

[ptex]

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}

 

[ptex]

Is 48 correct for the first one?