geelo Posts: 3, Reputation: 1 New Member #1 Jan 6, 2010, 02:52 AM
how do you write the equation for this sequence 3, -6, 12, -24?
I have an assignment and this is to find the equation of the sequence 3, -6, 12, -24? Please help me! Thanks
 Curlyben Posts: 18,482, Reputation: 1857 Admin & Wine Expert #2 Jan 6, 2010, 02:57 AM
What do you think the pattern is ?
 geelo Posts: 3, Reputation: 1 New Member #3 Jan 6, 2010, 03:25 AM
multiplying the preceding term by -2 to get the next term... but what is the equation?
 Curlyben Posts: 18,482, Reputation: 1857 Admin & Wine Expert #4 Jan 6, 2010, 03:28 AM
Well you've got it,
so
$x = ?$
 Unknown008 Posts: 8,076, Reputation: 723 Uber Member #5 Jan 6, 2010, 10:20 AM

Well, the general way to write the 'general solution of a sequence' of this type (geometric progression) is that way:

$T_n = ar^{n-1}$

where n is the n th term (for example T1 is first term, T2 second term, etc)
a is the first term
r is the common ratio

Well, you have Equations setting up:
$T_1 = 3 = (3)(r^{1-1})$
$T_2 = -6 = (3)(r^{2-1})$
$T_3 = 12 = (3)(r^{3-1})$

Those are enough to give the formula:

$T_n = (3)(-2^{n-1})$

Anyway, that's how you do it in higher classes if ever I made a wrong guess on your math level.
 geelo Posts: 3, Reputation: 1 New Member #6 Jan 14, 2010, 03:39 AM
Originally Posted by Unknown008
Well, the general way to write the 'general solution of a sequence' of this type (geometric progression) is that way:

$T_n = ar^{n-1}$

where n is the n th term (for example T1 is first term, T2 second term, etc)
a is the first term
r is the common ratio

Well, you have Equations setting up:
$T_1 = 3 = (3)(r^{1-1})$
$T_2 = -6 = (3)(r^{2-1})$
$T_3 = 12 = (3)(r^{3-1})$

Those are enough to give the formula:

$T_n = (3)(-2^{n-1})$

Anyway, that's how you do it in higher classes if ever I made a wrong guess on your math level.
thanks you very much for the equation...
have a nice day!
god bless! :)
 Unknown008 Posts: 8,076, Reputation: 723 Uber Member #7 Jan 15, 2010, 12:02 PM

You're welcome! :)

God bless too :)

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