Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 12 - Section 12.5 - Mathematical Induction - 12.5 Exercises - Page 878: 33

Answer

See explanations.

Work Step by Step

Step 1. Recall the property of Fibonacci sequence, we have: $F_{n}=F_{n-1}+F_{n-2}$ and $F_1=F_2=1$ Step 2. Prove the statement is true when $n=2$: $LHS=\begin{bmatrix} 1&1\\1&0 \end{bmatrix}\begin{bmatrix} 1&1\\1&0 \end{bmatrix}=\begin{bmatrix} 2&1\\1&1 \end{bmatrix}$, $RHS=\begin{bmatrix} F_3&F_2\\F_2&F_1 \end{bmatrix}=\begin{bmatrix} 2&1\\1&1 \end{bmatrix}=LHS$, thus it is true for $n=2$. Step 3. Assume the statement is true when $n=k$ ($k\gt2$): we have $\begin{bmatrix} 1&1\\1&0 \end{bmatrix}^k=\begin{bmatrix} F_{k+1}&F_k\\F_k&F_{k-1} \end{bmatrix}$ Step 4. Prove it is true for $n=k+1$: $LHS=\begin{bmatrix} 1&1\\1&0 \end{bmatrix}^{k+1}=\begin{bmatrix} F_{k+1}&F_k\\F_k&F_{k-1} \end{bmatrix}\begin{bmatrix} 1&1\\1&0 \end{bmatrix}=\begin{bmatrix} F_{k+1}+F_k&F_{k+1}\\F_k+F_{k-1}&F_k \end{bmatrix}=\begin{bmatrix} F_{k+2}&F_{k+1}\\F_{k+1}&F_k \end{bmatrix}$ With $n=k+1$, we have $RHS=\begin{bmatrix} F_{k+2}&F_{k+1}\\F_{k+1}&F_k \end{bmatrix}=LHS$ Thus, the statement is also true for $n=k+1$ Step 5. Conclusion: with mathematical induction, we have proved that the statement is true for all natural numbers $n$.
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