Solve the recurrence relations together with the initial

Samuel Desta

Samuel Desta

Answered question

2022-07-13

Solve the recurrence relations together with the initial conditions given. a. an = 7an−1 − 10an−2 , for n ≥ 2 , a0 = 2 , a1 = 1 .

Answer & Explanation

RizerMix

RizerMix

Expert2023-05-28Added 656 answers

To solve the given recurrence relation an=7an110an2 for n2, with initial conditions a0=2 and a1=1, we can use the method of characteristic equations.
Step 1: Find the characteristic equation by assuming a solution of the form an=rn.
Substituting this into the recurrence relation, we get:
rn=7rn110rn2.
Dividing both sides by rn2 (assuming r0), we have:
r2=7r10.
Step 2: Solve the characteristic equation to find the roots.
r27r+10=0.
This quadratic equation can be factored as (r5)(r2)=0.
So, the roots are r1=5 and r2=2.
Step 3: Write the general solution of the recurrence relation.
Since we have distinct roots, the general solution is given by:
an=c1·r1n+c2·r2n,
where c1 and c2 are constants determined by the initial conditions.
Step 4: Apply the initial conditions to find the specific solution.
Using the initial conditions a0=2 and a1=1, we can set up a system of equations:
a0=c1·r10+c2·r20=c1+c2=2,
a1=c1·r11+c2·r21=5c1+2c2=1.
Solving this system of equations, we find c1=1 and c2=3.
Step 5: Write the specific solution.
Substituting the values of c1 and c2 into the general solution, we obtain:
an=r1n+3r2n.
In this case, r1=5 and r2=2, so the specific solution is:
an=5n+3·2n.
Therefore, the solution to the given recurrence relation with the initial conditions a0=2 and a1=1 is an=5n+3·2n.

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