Question

Urgent (will give medal): If a1 = 1 and a2 = 1 and An = A n - 1 + A n - 2, then what is A4?

Thanks c:

Answer 1

Remember what we talked about before? Just plug in n=4 to get: \[\LARGE A_4=A_{4-1}+A_{4-2}\] This is just \[\LARGE A_4=A_3+A_2\] So now we have a2 but we still need a3, so just do the same thing with this formula like I just did for a4, An = A n - 1 + A n - 2

Answer 2

So:

A2 = A 2 - 1 + A 2 - 2? Which equals 1.

A3 = A 3 - 1 + A 3 - 2? Which also equals 3..

Then A4 = 5.