a + ar + ar^2 ...+ ar^(n-1)
a = 3
a r+ a r^2 = 60
r + r^2 = 20
r^2 + r - 20 = 0
(r-4)(r+5) = 0
r = 4
3 + 12 + 48 ....
3 * 4^(n-1)
The first term of a geometric sequence is 3 and the sum of the second and the third is 60 determine the first three terms and the general term
6 answers
Why did you use negative 5
I meant why didn't you use negative 5
Because when you multiply negative 5 and 4 you will get negative 20 but when you add you’ll get -1 .
So you have to multiply-4 with 5 to get -20 and when you add you get +1( the r is positive)
So you have to multiply-4 with 5 to get -20 and when you add you get +1( the r is positive)
Where does the "a" go
The first term of a geometric sequence is 3 and the sum of the second and the third is 60 determine the first three terms and the general term
1 answer