Find the first for terms of the sequence an=n(5n-6)

Question

a) -1,8,27,56

b)5,14,39,74

c)-1,8,21,44

d)5,-7,-13,-19

Answer 1

Beth,

 

To find the terms, plug n = 1, 2, 3, and 4 into the formula you have provided.

 

To get you started, if n = 1, then a₁ = 1(5·1-6) = -1.

 

This narrows down your answer to a) or c).

 

Good luck!

Answer 2

Just plug n=1, n=2, n=3, and n=4 into the equation and see what you get:

 

n      n(5n-5) = a_n

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1      1(5*1-6) = 1(5-6)=1*(-1) = -1

2      2(5*2-6) = 2(10-6)=2(4) = 8

3      3(5*3-6)=3(15-6)=3(9) = 27

4      4(5*4-6)=4(20-6)=4(14) = 56