Answer:
- geometric sequence with initial value 20 and common ratio 1/2
- average rate of change on [1, 3] = -7.5
Step-by-step explanation:
(a) The given points have sequential values of x and values of y that are each 1/2 the value before. The common ratio tells us the sequence is a geometric sequence.
(b) The first given point is (2, 10), so extrapolating backward, we determine the previous point to be ...
... (2-1, 10/(1/2)) = (1, 20)
Thus, we have enough information to determine the average slope between n=1 and n=3.
... (difference in y)/(difference in n) = (5 -20)/(3 -1) = -15/2 = -7.5
Take the logarithm of both sides. The base of the logarithm doesn't matter.
Drop the exponents:
Expand the right side:
Move the terms containing <em>x</em> to the left side and factor out <em>x</em> :
Solve for <em>x</em> by dividing boths ides by 5 log(4) - log(3) :
You can stop there, or continue simplifying the solution by using properties of logarithms:
You can condense the solution further using the change-of-base identity,