Question

write an expression to describe the rule for the pattern. 1, 4, 13, 40, 121, ...

Answer 1

Look at the difference

3 9 27 81
first term = 1
First term plus 3 3^1 = 4
second term plus 9 3^2 = 13
third term plus 27 3^3
fourth term plus 81 3^4

Can you write an expression for this. If you let term # = n

Answer 2

It is a linear sequence so we use a$d,since d=3 $a=1 depending on the terms,it increases by;a+(d raise to power N-1)

Answer 3

Sorry,they increase by the addition of their preceding term to D raise to power N-2