Step 1: Find the sum and product of the roots.
Given the quadratic equation x2−14x+36=0.
Let α and β be the roots.
Using Vieta's formulas:
Sum of roots: α+β=−(−14)/1=14
Product of roots: αβ=36/1=36
Step 2: Define a recurrence relation for Sn=αn+βn.
Since α and β are roots of x2−14x+36=0, they satisfy the equation:
α2−14α+36=0⟹α2=14α−36
β2−14β+36=0⟹β2=14β−36
Multiply the first equation by αn−2 and the second by βn−2 (for n≥2):
αn=14αn−1−36αn−2
βn=14βn−1−36βn−2
Adding these two equations:
αn+βn=14(αn−1+βn−1)−36(αn−2+βn−2)
Let Sn=αn+βn. The recurrence relation is:
Sn=14Sn−1−36Sn−2forn≥2
Step 3: Prove by induction that Sn is divisible by 2n.
Base Cases:
For n=1:
S1=α+β=14.
21=2.
14 is divisible by 2 (14=2×7). So, S1 is divisible by 21.
For n=2:
S2=α2+β2=(α+β)2−2αβ=(14)2−2(36)=196−72=124.
22=4.
124 is divisible by 4 (124=4×31). So, S2 is divisible by 22.
Inductive Hypothesis:
Assume that for some integer k≥1, Sk is divisible by 2k and Sk−1 is divisible by 2k−1.
This means Sk=ck⋅2k and Sk−1=ck−1⋅2k−1 for some integers ck and ck−1.
Inductive Step:
We need to show that Sk+1 is divisible by 2k+1.
Using the recurrence relation:
Sk+1=14Sk−36Sk−1
Substitute the inductive hypothesis:
Sk+1=14(ck⋅2k)−36(ck−1⋅2k−1)
Sk+1=(2⋅7)(ck⋅2k)−(4⋅9)(ck−1⋅2k−1)
Sk+1=7⋅ck⋅2k+1−9⋅ck−1⋅22⋅2k−1
Sk+1=7⋅ck⋅2k+1−9⋅ck−1⋅2k+1
Factor out 2k+1:
Sk+1=2k+1(7ck−9ck−1)
Since ck and ck−1 are integers, 7ck−9ck−1 is also an integer.
Therefore, Sk+1 is divisible by 2k+1.
By the principle of mathematical induction, αn+βn is divisible by 2n for all n=1,2,3,....
The final answer is Shownthatαn+βnisdivisibleby2nforn=1,2,3,...