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simba:
the second term of a geometric progression is 3 and the sum to infinity is 12
(i) find the first term of the progression



will someone solve it :)

simba:
q11 june 06 in part (i)  urgently plz

slvri:

--- Quote from: simba on October 14, 2009, 11:28:09 am ---the second term of a geometric progression is 3 and the sum to infinity is 12
(i) find the first term of the progression



will someone solve it :)


--- End quote ---
the nth term of a GP is given by an=arn-1
for the second term n=2
ar2-1=3
ar=3
a=3/r
the sum to infinity of a GP is given by S=a/(1-r)
a/(1-r)=12
a=12(1-r)
put a=3/r
3/r=12(1-r)
3=12r(1-r)
3=12r-12r2
12r2-12r+3=0
4r2-4r+1=0
(2r)2-2(2r)(1)+(1)2=0
(2r-1)2=0
2r-1=0
r=1/2
a=3/(1/2)=6
is this the correct answer?

Eamyzz:
yes i gt da same answer tooo  :)

simba:
guyz another question ....num.4 in nov.07

will someone help :???

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