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The sequence 6, -9, x , y is such that the first three terms form an arithmetic sequence and the last three terms form a geometric sequence. Find x and y.

 

Express answer as (x , y).

 Jun 17, 2019

Best Answer 

 #1
avatar+988 
+3

If the first three terms form an arithmetic sequence, the arithmetic sequence goes: 6, -9, x

 

Therefore, 6 - (-9) = -9 - x, x = -24

 

Since the last three terms is a geometric sequence, the geometric sequence goes: -9, -24, y

 

Therefore, -24/(-9)=y/(-24) 

 

After you solve for y, you get your answer.

 

Gavin, 

 Jun 17, 2019
 #1
avatar+988 
+3
Best Answer

If the first three terms form an arithmetic sequence, the arithmetic sequence goes: 6, -9, x

 

Therefore, 6 - (-9) = -9 - x, x = -24

 

Since the last three terms is a geometric sequence, the geometric sequence goes: -9, -24, y

 

Therefore, -24/(-9)=y/(-24) 

 

After you solve for y, you get your answer.

 

Gavin, 

GYanggg Jun 17, 2019

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