SOLUTION: Write a logarithmic equation Use f(x) = log5(x) as the parent function. Ordered pair (-3,-2) y =

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: Write a logarithmic equation Use f(x) = log5(x) as the parent function. Ordered pair (-3,-2) y =       Log On


   



Question 1153723: Write a logarithmic equation
Use
f(x) = log5(x)
as the parent function. Ordered pair (-3,-2)
y =

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


We can have function(s) of the form

log%285%2C%28x%2Bb%29%29%2Bc

Given that the function is to have an integer value at x=-3, we want -3+b to be a power of 5.

(a) first example
5^0 = 1; -3+b = 1 --> b = 4

log%285%2C%28-3%2B4%29%29+=+log%285%2C1%29+=+0

We want the function value at -3 to be -2, so we need to subtract 2. Our first function that satisfies the requirements is

log%285%2C%28x%2B4%29%29-2

A graph (window -10 to 10; -5 to 2):

graph%28400%2C400%2C-10%2C10%2C-5%2C2%2Clog%285%2C%28x%2B4%29%29-2%29

(b) second example
5^1 = 5; -3+b = 5 --> b = 8

log%285%2C%28-3%2B8%29%29+=+log%285%2C5%29+=+1

We want the function value at -3 to be -2, so we need to subtract 3. Our second function that satisfies the requirements is

log%285%2C%28x%2B8%29%29-3

A graph (window -10 to 10; -5 to 2), showing both graphs passing through (-3,-2):



We can also have functions of the form

a%2Alog%285%2C%28x%2Bb%29%29

Again using b=8,

log%285%2C%28-3%2B8%29%29+=+log%285%2C5%29+=+1

We want the function value to be -2 at x=-3; so we can multiply this function by -2. Our third function that satisfies the requirements is

%28-2%29%2Alog%285%2C%28x%2B8%29%29

A graph again, showing the graphs of all three functions passing through (-3,-2):



You should be able to see that we can get as many functions as we want that satisfy the requirement.

Here is one more that gives the value -2 at x=-3:

%28-5%29%2Alog%285%2C%28x%2B8%29%29%2B3

One more graph, showing all four functions passing through (-3,-2):