AnswersKISD SS-3350B-Algebra I B-CRUnit Test

Exponential Decay Functions Answers

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Which is the graph of f(x) = 5(2)x?

A
On a coordinate plane, an exponential growth function approaches y = 0 in the second quadrant and goes through points (0, 5) and (2, 20).
Option A
B
On a coordinate plane, an exponential growth function approaches y = 0 in the second quadrant and goes through points (0, 2) and (2, 50).
Option B
C
On a coordinate plane, an exponential growth function approaches y = 0 in the second quadrant and goes through points (0, 2) and (2, 10).
Option C
D
On a coordinate plane, an exponential growth function approaches y = 0 in the second quadrant and goes through points (0, 5) and (2, 10).
Option D
2
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Geraldine is asked to explain the limits on the range of an exponential equation using the function f(x) = 2x. She makes these two statements:1. As x increases infinitely, the y-values are continually doubled for each single increase in x.2. As x decreases infinitely, the y-values are continually halved for each single decrease in x.

A
Statement 1 is incorrect because the y-values are increased by 2, not doubled.
B
Statement 2 is incorrect because the y-values are doubled, not halved.
C
The conclusion is incorrect because the range is limited to the set of integers.
D
The conclusion is incorrect because the range is limited to the set of positive real numbers.
3

After years of maintaining a steady population of 32,000, the population of a town begins to grow exponentially. After 1 year and an increase of 8% per year, the population is 34,560. Which equation can be used to predict, y, the number of people living in the town after x years? (Round population values to the nearest whole number.)

A
y = 32,000(1.08)x
B
y = 32,000(0.08)x
C
y = 34,560(1.08)x
D
y = 34,560(0.08)x
4

A collector’s item is purchased for $150 and its value increases by 3% each year. Which graph can be used to determine approximately how many years it will take for the value to double?

A
Option
B
Option
C
Option
D
Option
5

How would the graph change if the b value in the equation is decreased but remains greater than 1? Check all that apply.

A
The graph will begin at a lower point on the y-axis.
B
The graph will increase at a faster rate.
C
The graph will increase at a slower rate.
D
The y-values will continue to increase as x-increases.
E
The y-values will each be less than their corresponding x-values.
6

A function of the form f(x) = abx is modified so that the b value remains the same but the a value is increased by 2. How do the domain and range of the new function compare to the domain and range of the original function? Check all that apply.The range stays the same. The range becomes y > 2.The domain stays the same. The domain becomes x > 2.The range becomes y ≥ 2.The domain becomes x ≥ 2.

A
The range stays the same.
B
The range becomes y > 2.
C
The domain stays the same.
D
The domain becomes x > 2.
E
The range becomes y ≥ 2.
F
The domain becomes x ≥ 2.
7

Which equation represents an exponential function that passes through the point (2, 80)?

A
f(x) = 4(x)5
B
f(x) = 5(x)4
C
f(x) = 4(5)x
D
f(x) = 5(4)x
8

The value of a collector’s item is expected to increase exponentially each year. The item is purchased for $500 and its value increases at a rate of 5% per year. Find the value of the item after 4 years.

A
$578.81
B
$607.75
C
$1687.50
D
$2531.25
9

A limited-edition poster increases in value each year with an initial value of $18. After 1 year and an increase of 15% per year, the poster is worth $20.70. Which equation can be used to find the value, y, after x years? (Round money values to the nearest penny.)

A
y = 18(1.15)x
B
y = 18(0.15)x
C
y = 20.7(1.15)x
D
y = 20.7(0.15)x
10

Which best describes the graph of the function f(x) = 4(1.5)x?

A
The graph passes through the point (0, 4), and for each increase of 1 in the x-values, the y-values increase by 1.5.
B
The graph passes through the point (0, 4), and for each increase of 1 in the x-values, the y-values increase by a factor of 1.5.
C
The graph passes through the point (0, 1.5), and for each increase of 1 in the x-values, the y-values increase by 4.
D
The graph passes through the point (0, 1.5), and for each increase of 1 in the x-values, the y-values increase by a factor of 4.
11

An account with a $250 balance accrues 2% annually. If no deposits or withdrawals are made, which graph can be used to determine approximately how many years will it take for the balance to be $282?

A
Option
B
Option
C
Option
D
Option
12

A growth medium is inoculated with 1,000 bacteria, which grow at a rate of 15% each day. What is the population of the culture 6 days after inoculation?

A
y = 1,000(1.15)6; 2,313 bacteria
B
y = 1,000(1.15)7; 2,660 bacteria
C
y = 1,000(1.5)5; 7,594 bacteria
D
y = 1,000(1.5)6; 11,391 bacteria
13

Which graph shows exponential growth?

A
On a coordinate plane, a parabola opens up with vertex at (0, 0).
Option A
B
On a coordinate plane, a curve approaches y = 0 in quadrant 2 and curves up into quadrant 1.
Option B
C
On a coordinate plane, a straight line with positive slope crosses the y-axis at (negative 1, 0) and crosses the y-axis at (2, 0).
Option C
D
On a coordinate plane a curve opens down and to the right in quadrants 1 and 4. It crosses the x-axis at (1, 0).
Option D
14

On a coordinate plane, an exponential function approaches y = 0 in quadrant 2 and curves up and increases in quadrant 1.

Question illustration
A
The domain includes all integers, and the range is y ≥ 0.
B
The domain includes all integers, and the range is y > 0.
C
The domain includes all real numbers, and the range is y ≥ 0.
D
The domain includes all real numbers, and the range is y > 0.
15

A 2-column table has 5 rows. The first column is labeled x with entries negative 1, 0, 1, 2, 3. The second column is labeled y with entries one-tenth, one-half, five-halves, StartFraction 25 Over 2 EndFraction, StartFraction 125 Over 2 EndFraction

Question illustration
A
Twelve-fifths
Option A
B
5
C
StartFraction 25 Over 2 EndFraction
Option C
D
25

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