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# C2 geometric series Ex 7F question 8 watch

1. A sequence of numbers, u1,u2,u3....un,..... is given by the formula un= 3(2/3)^n -1 where n is a positive integer.
a) Find u1, u2 and u3
b) show that the sum of 15 un= -9.014 where n=1
c) prove that u = 2(2/3)^n -1
n+1
2. (Original post by gingeninge)
A sequence of numbers, u1,u2,u3....un,..... is given by the formula un= 3(2/3)^n -1 where n is a positive integer.
a) Find u1, u2 and u3
b) show that the sum of 15 un= -9.014 where n=1
c) prove that u = 2(2/3)^n -1
n+1
Is that or ?
3. (Original post by joostan)
?
the latter of the two
4. (Original post by gingeninge)
the latter of the two
How good is your sigma manipulation?
The original is the same as:
5. OMG how did i miss that! thank you so much :-) :-)
6. (Original post by gingeninge)
OMG how did i miss that! thank you so much :-) :-)
NP

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Updated: April 14, 2013
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