View Full Version : How do you write the equation for this sequence 3, -6, 12, -24?
geelo
Jan 6, 2010, 02:52 AM
I have an assignment and this is to find the equation of the sequence 3, -6, 12, -24? Please help me! Thanks
Curlyben
Jan 6, 2010, 02:57 AM
What do you think the pattern is ?
geelo
Jan 6, 2010, 03:25 AM
multiplying the preceding term by -2 to get the next term... but what is the equation?
Curlyben
Jan 6, 2010, 03:28 AM
Well you've got it,
so
x = ?
Unknown008
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
Jan 14, 2010, 03:39 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.
thanks you very much for the equation...
have a nice day!
god bless! :)
Unknown008
Jan 15, 2010, 12:02 PM
You're welcome! :)
God bless too :)