Question

What is the sum of the first 12 terms in the fibonacci sequence?

Answer 1

Hello,

$u_{1} =a\\ u_{2} =b\\ u_{3} =a+b\\ u_{4} =a+2b\\ u_{5} =2a+3b\\ u_{6} =3a+5b\\ u_{7} =5a+8b\\ u_{8} =8a+13b\\ u_{9} =13a+21b\\ u_{10} =21a+34b\\ u_{11} =34a+55b\\ u_{12} =55a+89b\\ \boxed{\sum_{i=1}^{12}(u_i)=144a+232b\\}$