SOLUTION: I am not understanding sequences and series? Can someone help me understand this better and show the steps. Solve question given that a3 = 3 then a6= -81 Find r? Find a1. Th

Question 204901: I am not understanding sequences and series? Can someone help me understand this better and show the steps. Solve question given that a3 = 3 then a6= -81 Find r? Find a1. Thank you

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
given that a3 = 3 then a6= -81 Find r? Find a1
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Since you are looking for "r" your series is a geometric series.
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a3 = a1*r^2 = 3
a6 = a1*r^5 = -81
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Divide a6 by a3 to get:
r^3 = -27
r = -3
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Substitute r = -3 into a3 to solve for a1
a1*(-3)^2 = 3
a1 = 3/9 = 1/3
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Cheers,
Stan H.
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