dexlessmalyk
Name: (specify a nickname)
IGN: TimesEye
Job: Sniper
Level: 104
Number of posts: 38
Registration date: 2008-05-13
 |  Subject: Geometric Sequence ?????????????  Tue Sep 16, 2008 3:08 pm | |
| I know the formula is a n=a 1r n-1but in order to do that u need a ratio(r) and a first term (a 1) and i have term 3 and tem 6 they were given to me in the problem a 3= 180, a 6=38,880 i need to find the ratio and the 1st term  |
|
SpikeAi
Name: Neal
IGN: SpikeAi
Job: Bow Master
Level: 151
Number of posts: 737
Registration date: 2008-04-21
| | Subject: Re: Geometric Sequence ????????????? Tue Sep 16, 2008 4:01 pm | |
| Uhh not sure if you will understand my logic or if it is what the teacher wants to see..
between a3 and a6 there are 3 multiplications all by the same value x.
Therefore 180 * x * x * x = 38880
Or 180* x^3 = 38880
x^3 = 38880/180
x^3 = 216
x = cube root of 216
x = 6 |
|
Loveable Kaze
Name: David
IGN: Kazegenso (retired)
Job: Writer
Level: up! =D
Number of posts: 1208
Registration date: 2007-06-19
Mood: Speechless!
| | Subject: Re: Geometric Sequence ????????????? Tue Sep 16, 2008 4:24 pm | |
| I never learned this in my Geometry class....o_O" It's quite interesting... |
|
Bilbo
Administrator
Name: Daniel
IGN: TheBilbo
Job: Dark Knight
Level: 160
Number of posts: 1818
Registration date: 2008-03-20
Mood: pretending to be a Hobbit
| | Subject: Re: Geometric Sequence ????????????? Wed Sep 17, 2008 12:00 am | |
| use the formula and make two equations with two unknowns, a1 and r:
180 = a1 * r2 (squared)
a1 = 180/r2
substitute in 2nd equation:
38,880 = a1 * r5 (power 5)
38,880 = 180/r2 * r5
38,888 = 180 * r3
r3 = 38,880/180 = 216
r = 6
a1 = 180/36 = 5 _____________________  |
|
