1,1,2,3,5,8,13,21,34,55,89,⋯
The above is the Fibonacci sequence, where Fn is the nth Fibonacci number with F1=F2=1.
Without using a calculator, find which answer is equivalent to (F10)2−(F9)2.
Hint: Try to find a simpler formula for (Fn+1)2−(Fn)2.