Pearson Algebra 2 Common Core, 2011
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Pearson Algebra 2 Common Core, 2011 View details
End-of-Course Assessment

Exercise 14 Page 965

What is the general form of an exponential function?

G

Practice makes perfect

We are asked to write a function to represent the following graph.

Notice that this is a graph of an exponential function. Therefore, it needs to be in the following form. f(x) = a * b^xIn this form a represents the y-intercept. As we can see from the graph, our y-intercept is -2. Therefore, the value of a is -2. f(x) = - 2 * b^x If we examine the given options we can see that all b values are 3. By knowing this we will examine the remaining two options G and I by checking for an arbitrary point. Let's randomly choose x= - 4 and then substitute into these options to see the corresponding outputs. Let's begin with option I.

f(x)= -2* 3^(- x)
f( -4)= -2* 3^(- ( -4))
â–¼
Evaluate right-hand side
f(-4)=-2* 3^4
f(-4)=-2* 81
f(-4)=- 162

We can see from the graph that the value of -4 is approximately 0. Therefore, we can eliminate option I also. Last, let's check option G.

f(x)= -2* 3^x
f( -4)= -2* 3^(-4)
â–¼
Evaluate right-hand side
f(-4)= -2* 1/3^4
f(-4)= -2* 1/81
f(-4)=-2/81
f(-4)= - 0.024691 ...
f(-4) ≈ 0

Great! We get approximately 0 for the value of f(-4). We can conclude that our exponent needs to be positive x. f(x) = - 2 * 3^x Therefore, our answer is option G.