math!
posted by Anonymous
determine two geometreic sequences whose first terms are 18x9, 2x+8 and x1
how would I go about and do this question?
I have no idea! so a little help would be really helpful! thanks!
A geometric sequence looks like
a, ar, ar^{2}, ar^{3}, ..., ar^{n}, ...
where a is usually called the base and r is the common ratio.
If the first three terms are 18x9, 2x+8 and x1 then
(2x+8)/(18x9) = (x1)/(2x+8)
i.e., the ratio of t_{n}/t_{n1} is the common ratio.
So solve
(2x+8)*(2x+8)=(18x9)*(x1) for x.
Then substitute the values of x into the first 3 terms to determine what they are, then follow the above to determine the common ratio, the base, then the general or n^{th} term.
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