# Proof for nth term formulaWatch

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16 years ago
#21
(Original post by aacharyauk)
OK -im really sorry. Right ummmmm
I used this formula to get the nth term of this series

1,3,6,10,15

here i had to look at the third difference to get a constant and hence the formula became
a + (n-1)d + (1/2)(n-1)(n-2)c1 + 1/6 (n-1)(n-2)(n-3)

and for this series

1, 5, 14, 30, 55

the formula remained as it was as at the second difference i had a constant.

Now i had to prove why this formula works for working out the nth term.
are these diagonals of the pascal triangle?
0
#22
(Original post by aacharyauk)
OK -im really sorry. Right ummmmm
I used this formula to get the nth term of this series

1,3,6,10,15

here i had to look at the third difference to get a constant and hence the formula became
a + (n-1)d + (1/2)(n-1)(n-2)c1 + 1/6 (n-1)(n-2)(n-3)

and for this series

1, 5, 14, 30, 55

the formula remained as it was as at the second difference i had a constant.

Now i had to prove why this formula works for working out the nth term.
it should read - a + (n-1)d + (1/2)(n-1)(n-2)c1 + 1/6 (n-1)(n-2)(n-3)c2
0
#23
u mean the coursework-
its somit bout squares in rectangles
0
16 years ago
#24
The series 1,5, 14, 30, 55. has first difference 4, thus change in difference 5 between terms. But 14 + 14 is not equal to 30, am i missing something?
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#25
(Original post by theone)
The series 1,5, 14, 30, 55. has first difference 4, thus change in difference 5 between terms. But 14 + 14 is not equal to 30, am i missing something?
because it goes onto the third difference

the two sequences i gave u are completely separate
they dont link in any way between the two.
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#26
(Original post by aacharyauk)
because it goes onto the third difference

the two sequences i gave u are completely separate
they dont link in any way between the two.
u dont need to fo 14+14
the first differences go 4,9,16,25 and the second differences go 5,7,9 and the third difference is constant at 2.
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16 years ago
#27
Eeek. I did that investigation and I had to find some degree level maths stuff about limits to prove my formula.
0
16 years ago
#28
Actually, I don't think this wasn't the one I did. This isn't the fencing one is it?
0
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