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October 21, 2014

October 21, 2014

Posted by **Lucas** on Sunday, February 3, 2013 at 4:35pm.

2..a new sequence is formed by adding together the corresponding terms of a geometric sequence and an arithmetic sequence.The common ratio of the geometric sequence is 2 and the common difference of the arithmetic sequence is 2.The first term of the new sequence is 1,and the second term is 7...

2.1 calculate the third term of the new sequence

2.2write down an expression for the n-th term of the new sequence

- Maths -
**Steve**, Sunday, February 3, 2013 at 5:23pma+d = ar

a = 12

r < 1

3/2 (2a+2d) = a(1+r+r^2) - 4/3

3ar = a(1+r+r^2) - 4/3

36r = 12(1+r+r^2) - 4/3

r = 2/3 or 4/3

r=2/3:

12+d = 12* 2/3

d = -4

AP = 12 8 4 0 ...

GP = 12 8 16/3 32/9 ...

check

12+8+4 = 12+8+16/3 - 4/3 YES

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