All ACT Math Resources
Example Questions
Example Question #11 : How To Find The Domain Of A Function
What is the domain of the following function?
The two potential concerns for domain in a standard function are negative numbers inside even-powered radicals, and dividing by zero. In this case, the radical we have is odd-powered, so having a negative result underneath the radical is fine. All we need to do, then, is avoid dividing by zero, which means avoiding a result which sums to zero under the radical. In this case, only  will create this situation, so we must avoid it.
Thus, our domain isÂ
Example Question #12 : How To Find The Domain Of A Function
Find the domain of the following function:
To find the domain, you must find the values for which you can plug in for . Based on the given function, you know that you can not have a demoninator equal to
. So, by setting the denominator equal to
, you can find out the values that can not be in the domain, and then simply remove them from your set of numbers from negative infinity to positive infinity.
Thus,
Therefore, for our function, Â can not equal
 or it will be undefined. Thus, we get the set of numbers excluding positive
.
Example Question #1 : How To Find Domain And Range Of The Inverse Of A Relation
Define function  as follows:
Suppose the domain of were to be restricted so thatÂ
 could have an inverse. Which of the following restrictions would not giveÂ
 an inverse?
None of the other responses gives a correct answer.
 has an inverse on a given domain if and only if there are no two distinct values on the domainÂ
 such thatÂ
.
The key to this question is to find the zeroes of the polynomial, which can be done as follows:
'
The zeroes are .Â
 has one boundary that is a zero and one interior point that is a zero. Therefore, there is a vertex in the interior of the interval, so it will have at least one pairÂ
 such thatÂ
. Since a cubic polynomial has two "arms", one going up and one going down,Â
 will increase asÂ
 increases in the other four intervals.Â
 is the correct choice.
Example Question #2 : How To Find Domain And Range Of The Inverse Of A Relation
Define function  as follows:
Suppose the domain of were to be restricted so thatÂ
 could have an inverse. Which of the following restrictions would not giveÂ
 an inverse?
 has an inverse on a given domain if and only if there are no two distinct values on the domainÂ
 such thatÂ
.
 has a sinusoidal wave as its graph, with periodÂ
 and phase shiftÂ
 units to the left. Its positive "peaks" and  "valleys" begin atÂ
 and occur everyÂ
 units.
Since  includes one of these "peaks" or "valleys", it contains at least two distinct valuesÂ
 such thatÂ
. It is the correct choice.
Example Question #11 : Algebraic Functions
Define function  as follows:
On which of the following restrictions of the domain of  wouldÂ
 not exist?
None of the other responses gives a correct answer.
 has an inverse on a given domain if and only if there are no two distinct values on the domainÂ
 such thatÂ
.
 is a quadratic function, so its graph is a parabola. The key is to find the
-intercept of the vertex of the parabola, which can be found by completing the square:
The vertex happens at , so the interval which contains this value will have at least one pairÂ
 such thatÂ
. The correct choice isÂ
.
Example Question #12 : Algebraic Functions
Define function  as follows:
On which of the following restrictions of the domain of  wouldÂ
 not exist?
 has an inverse on a given domain if and only if there are no two distinct values on the domainÂ
 such thatÂ
.
 has a sinusoidal wave as its graph, with periodÂ
; it begins at a relative maximum ofÂ
 and has a relative maximum or minimum everyÂ
 units. Therefore, any interval containing an integer multiple ofÂ
 will have at least two distinct valuesÂ
 such thatÂ
.
The only interval among the choices that includes a multiple of  isÂ
:
 .
This is the correct choice.
Example Question #5 : How To Find Domain And Range Of The Inverse Of A Relation
Define function  as follows:
In which of the following ways could the domain of  be restricted so that
 does not have an inverse?
None of the other responses give a correct answer.
None of the other responses give a correct answer.
If , thenÂ
. By the addition property of inequality, ifÂ
, thenÂ
. Therefore, ifÂ
,Â
.Â
Consequently, there can be no  such thatÂ
, regardless of how the domain is restricted.Â
 will have an inverse regardless of any domain restriction.
Example Question #6 : How To Find Domain And Range Of The Inverse Of A Relation
Consider the following statement to be true:Â
   If a fish is a carnivore, then it is a shark.
Â
Which of the following statements must also be true?
If a fish is not a shark, then it is a carnivore.
If a fish is a shark, then it is a carnivore.
If a fish is not a shark, then it is not a carnivore.
All fish are sharks.
If a fish is not a carnivore, then it is not a shark.
If a fish is not a shark, then it is not a carnivore.
The statement "If a fish is a carnivore, then it is a shark", can be simplified to "If X, then Y", where XÂ represents the hypothesis (i.e. "If a fish is a carnivore...") and YÂ represents the conclusion (i.e. "...then it is a shark").
Answer choice A is a converse statement, and not necessarily true: ("If Y, then X").
Answer choice C is an inverse statement, and not necessarily true: ("If not X, then not Y").
Answer choice D states "If not Y, then X", which is false.
Answer choice E "All fish are sharks" is also false, and cannot be deduced from the given information.
Answer choice B is a contrapositive, and is the only statement that must be true. "If not Y, then not X."
The statement given in the question suggests that all carnivorous fish are sharks. So if a fish is not a shark then it cannot be carnivorous.
Example Question #1 : Algebraic Functions
If f(x)=3x and g(x)=2x+2, what is the value of f(g(x)) when x=3?
Â
20
22
18
24
24
With composition of functions (as with the order of operations) we perform what is inside of the parentheses first. So, g(3)=2(3)+2=8 and then f(8)=24.
Â
Â
Â
Example Question #2 : Algebraic Functions
g(x) = 4x – 3
h(x) = .25Ď€x + 5
If f(x)=g(h(x)). What is f(1)?
19π – 3
13Ď€ + 3
Ď€ + 17
42
4
Ď€ + 17
First, input the function of h into g. So f(x) = 4(.25πx + 5) – 3, then simplify this expression f(x) = πx + 20 – 3 (leave in terms of π since our answers are in terms of π). Then plug in 1 for x to get π + 17.
All ACT Math Resources
