Question

Help with Sequences?

Answer 1

The following function defines a recursive sequence:

f(0) = -3

f(1) = 6

f(n) = -2 x f(n -1) - f(n - 2); for n > 1

Which of the following sequences is defined by this recursive function?

-3, 6, -9, -12, …
-3, 20, -95, 480, …
-3, 6, -9, 12, …
-3, -20, -95, -480, …

Answer 2

@Directrix

Answer 3

you can plug in numbers

Answer 4

f(0) = -3
f(1) = 6

that rules out two of the answers

Answer 5

Would it be D?

Answer 6

@perl

Answer 7

@Directrix @iGreen

Answer 8

Is this -2 --> -2 x f(n -1) - f(n - 2)

supposed to be just -2 times f(n-1) or could it be -2 times {f(n -1) - f(n - 2)} ?

Answer 9

Yes, it is -2 x f(n -1) - f(n - 2)

Answer 10

So, for this: -3, 20, -95, 480, …

480 would have to be equal to -2* -95 - 20.
Let's see.
480 =? 190 - 20 NO, That option is not correct.

Answer 11

Oh! Would it be C ?

Answer 12

-2 x -9 - 6 = 12.

Answer 13

Yes, the third option is what I got: -3, 6, -9, 12, …

Answer 14

It was correct.

Answer 15

Good to hear that.