The Fibonacci sequence is defined by

Question:

The Fibonacci sequence is defined by

$\mathrm{l}=\mathrm{a}_{1}=\mathrm{a}_{2}$ and $\mathrm{a}_{\mathrm{n}}=\mathrm{a}_{\mathrm{n}-1}+\mathrm{a}_{\mathrm{n}-2}, \mathrm{n}>2$

Find $\frac{\mathrm{a}_{\mathrm{n}+1}}{\mathrm{a}_{\mathrm{n}}}$, for $\mathrm{n}=1,2,3,4,5$

Solution:

$\mathrm{l}=\mathrm{a}_{1}=\mathrm{a}_{2}$

$\mathrm{a}_{\mathrm{n}}=\mathrm{a}_{\mathrm{n}-1}+\mathrm{a}_{\mathrm{n}-2}, \mathrm{n}>2$

$\therefore \mathrm{a}_{3}=\mathrm{a}_{2}+\mathrm{a}_{1}=1+\mathrm{l}=2$

$\mathrm{a}_{4}=\mathrm{a}_{3}+\mathrm{a}_{2}=2+1=3$

$\mathrm{a}_{5}=\mathrm{a}_{4}+\mathrm{a}_{3}=3+2=5$

$\mathrm{a}_{6}=\mathrm{a}_{5}+\mathrm{a}_{4}=5+3=8$

$\therefore$ For $\mathrm{n}=1, \frac{\mathrm{a}_{\mathrm{n}}+1}{\mathrm{a}_{\mathrm{n}}}=\frac{\mathrm{a}_{2}}{\mathrm{a}_{1}}=\frac{1}{1}=1$

For $\mathrm{n}=2, \frac{\mathrm{a}_{\mathrm{n}}+\mathrm{l}}{\mathrm{a}_{\mathrm{n}}}=\frac{\mathrm{a}_{3}}{\mathrm{a}_{2}}=\frac{2}{1}=2$

For $\mathrm{n}=3, \frac{\mathrm{a}_{\mathrm{in}}+1}{\mathrm{a}_{\mathrm{n}}}=\frac{\mathrm{a}_{4}}{\mathrm{a}_{3}}=\frac{3}{2}$

For $\mathrm{n}=4, \frac{\mathrm{a}_{\mathrm{n}}+1}{\mathrm{a}_{\mathrm{n}}}=\frac{\mathrm{a}_{5}}{\mathrm{a}_{4}}=\frac{5}{3}$

For $\mathrm{n}=5, \frac{\mathrm{a}_{\mathrm{n}}+1}{\mathrm{a}_{\mathrm{n}}}=\frac{\mathrm{a}_{6}}{\mathrm{a}_{5}}=\frac{8}{5}$

Leave a comment

Close

Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now