Question

Which recursive definition produces an arithmetic sequence where g(5) = 8 and g(10) = 10?

Answer 1

Answer:

gₙ = gₙ₋₁ + 0.4, with g₁ = 6.4

Step-by-step explanation:

The n-th term of an arithmetic sequence can be written as:

gₙ = g₁ + (n - 1)*d

Where g₁ is the first value, and d is the difference between any two consecutive terms of this sequence.

Then we have the equations:

g₅ = 8 = g₁ + (5 -1)*d

g₁₀ = 10 = g₁ + (10 - 1)*d

This is a system of equations, we can rewrite this as:

8 = g₁ + 4*d

10 = g₁ + 9*d

To solve this, the first step will be isolate one of the variables in one of the equations, i will isolate g₁ in the first equation:

g₁ = 8 - 4*d

Now we can replace this in the second equation to get:

10 = 8 - 4*d + 9*d

10 = 8 + 5*d

10 - 8 = 5*d

2 = 5*d

2/5 = d = 0.4

Now with this, we can find the value of g₁ by using the equation:

g1 = 8 - 4*d = 8 - 4*(2/5) = 8 - 8/5 = 6.4

Then the nth term of this sequence can be written as:

gₙ = 6.4 + (n - 1)*0.4

This relation also can be written as:

gₙ = gₙ₋₁ + d = gₙ₋₁ + 0.4, with g₁ = 6.4

Then the correct option is the second option.