Question

.I need to find a rule for .the inputs: 1,2,3,4 and the outputs:3,9,18,30.

Please Help! Thanks

Answer 1

1 3

2 9
3 18
4 30

I then doubled the 2nd column

1 6 = 3 x 1 x 2
2 18 = 3 x 2 x 3
3 36 = 3 x 3 x 4
4 60 = 3 x 4 x 5
...
n ---- 3n(n+1)
but we had doubled everything

so f(x) = 3x(x+1)/2 or (3/2)x(x+1)