SOLUTION: Please help me with this 1, 4, 9, 16, 2, -6, 18, 54 8, 4, 2, 1, X, x+y, x+ 2y 2, 5, 10, 17

Algebra ->  Sequences-and-series -> SOLUTION: Please help me with this 1, 4, 9, 16, 2, -6, 18, 54 8, 4, 2, 1, X, x+y, x+ 2y 2, 5, 10, 17      Log On


   

Question 1038698: Please help me with this
1, 4, 9, 16,
2, -6, 18, 54
8, 4, 2, 1,
X, x+y, x+ 2y
2, 5, 10, 17
Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
.
Please help me with this highlight%28with_what_question_sign%29 

1, 4, 9, 16,         a%5Bn%5D = n%5E2, n = 1, 2, 3, 4

2, -6, 18, 54 

8, 4, 2, 1,          Geom. progression, a%5Bn%5D = 8%2A%281%2F2%29%5E%28n-1%29, n= 1, 2, 3, 4

X, x+y, x+ 2y        Arithm. progression of three terms
   
2, 5, 10, 17         Consider the differences - they form an arithm. progression 3, 5, 7.