SOLUTION: The common ratio of a geometric sequence is -3. If the terms of these sequence are 3y, y+6, a+1, ..., respectively. What is the value of a?

Question 955461: The common ratio of a geometric sequence is -3. If the terms of these sequence are 3y, y+6, a+1, ..., respectively. What is the value of a?
Found 2 solutions by josgarithmetic, stanbon:
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!

You would know what to do if you understand that system of equations.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The common ratio of a geometric sequence is -3. If the terms of these sequence are 3y, y+6, a+1, ..., respectively. What is the value of a?
Equations:
(y+6)/(3y) = -3
y + 6 = -9y
10y = -6
y = -3/5
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(a+1)/(y+6) = -3
(a+1)/((-3/5)+(30/5)) = -3
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(a+1)/(27/5) = -3
a+1 = -81/5
a = -86/5
a = -17 1/5
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Cheers,
Stan H.
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