Qualification > Math

Finding the nth term

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NotAbod:
hello,
for some questions, finiding the nth term is hard!!!
is there a formula or something to find the nth term?
For the Sequence: 17, 26, 37, 50, 65, ......
Wat is the nth term?
how did u find it?
help me please  ::) ::)
Thanks in advance.

Most UniQue™:
If the differences are same the formula is this:
a+(n-1)d, a is the first term of the sequence and d is the common difference between the numbers. n is our term number and we plug the term number instead of n to find the value of the term.

If the differences are changing then we use this formula:

nth term = a + (n - 1)d + ½(n - 1)(n - 2)c

This time there is a letter c which stands for the second difference (or the difference between the differences and d is just the difference between the first two numbers.

Ok so we will use the 2nd formula to your question since the difference between the numbers are changing:

the difference is: 9,11,13,15
the difference between the differences:2,2,2,2

a=17
d=9(difference between the first two numbers,17 and 26)
c=2(the difference between the differences)

plug in these values into the formula:

a + (n - 1)d + ½(n - 1)(n - 2)c

17+(n-1)9+1/2(n-1)(n-2)2
simplify it and u will get: n^2+6n+10
In order to see if ur formula is right u can do it like this:
nth term=1---> 1^2 +6(1)+10=17
nth term=2---> 2^2 +6(2)+10=26
nth term=3---> 3^2 +6(3)+10=37

I hope you will get it ;D

NotAbod:
nvm, both r correct  :D

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