All GMAT Math Resources
Example Questions
Example Question #54 : Functions/Series
Define two real-valued functions as follows:
Determine .
by definition.
is piecewise defined, with one defintion for negative values of the domain and one for nonnegative values.
If , then we use the definition . This happens if
or
Therefore, the defintion of for or is
Subsquently, if , we use the defintion , since :
.
The correct choice is
Example Question #53 : Understanding Functions
Define a function on the real numbers as follows:
Give the range of the function.
This can be understood better by substituting , and, subsequently, in the function's definition.
which is now in standard quadratic form in terms of .
Write this in vertex form by completing the square:
Substitute back for , and the original function can be rewritten as
.
To find the range, note that . Therefore,
and
The range of is the set .
Example Question #58 : Functions/Series
Define a function on the real numbers as follows:
Give the range of the function.
This can be understood better by substituting , and, subsequently, in the function's definition.
which is now in standard quadratic form in terms of .
Write this in vertex form by completing the square:
Substitute back for . The original function can be rewritten as
or, in radical form,
can assume any real value; so, subsequently, can . But its square must be nonnegative, so
and
The range of is
Example Question #54 : Understanding Functions
If the functions and intersect only when , and that , and , what is ?
None of the other answers.
In order to find exactly the values where the equations intersect and when . We need to consider each piece of information seperately.
Let's start with . Plugging into , we have . Plugging 0 into this, we have. This in turn equals 1, because we were given that piece of information in the beginning. So we end up with
Now let's shift our attention to "intersect only when " That means, if we plug 1 into both equations, we can set them equal to each other.
becomes becomes .
Now we have two different equations arising from the two previous paragraphs.
We can solve this system of equations using the substitution method.
Solving for in the first equation gives .
Plugging this equation in for the 2nd equation gives . Using algebra on this equation we get
Now we are ready to use the quadratic formula to solve for .
Finally, since we're told in the beginning that , we must pick the plus sign in our solution for . Hence
.
Example Question #55 : Understanding Functions
Define two real-valued functions as follows:
Determine .
The correct answer is not given among the other responses.
This question is asking us to find the composition of f and g. In order to do this we need to plug g(x) into the x value in f(x).
Example Question #1281 : Gmat Quantitative Reasoning
A sequence is formed the same way the Fibonacci sequence is formed. Its third and fourth terms are 16 and 30, respectively. What is its first term?
A Fibonacci-style sequence starts with two numbers, with each successive number being the sum of the previous two. The second term is therefore the difference of the fourth and third terms, and the first term is the difference of the third and second.
Second term:
First term:
Example Question #62 : Functions/Series
Define two real-valued functions as follows:
Determine .
The correct answer is not among the other responses.
The correct answer is not among the other responses.
This is not among the given choices.
Example Question #63 : Functions/Series
Define function as follows:
has an inverse on each of the following domains except:
has an inverse on a given domain if and only if there are no two distinct values on the domain such that .
The key to this question is to find the zeroes of the polynomial, which can be done as follows:
The zeroes are , or approximately .
The polynomial being cubic, its graph has two vertices; since all three zeroes are in the interval , so are both vertices. Therefore, this interval must have at least one pair such that . Since a cubic polynomial has two "arms", one going up and one going down, will continuously increase or decrease over the other intevals. The correct choice is .
Example Question #64 : Functions/Series
Define function as follows:
has an inverse on each of the following domains except:
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 domain such that .
If , then can be defined to be .
This happens if
, or
Similarly, if , can be defined to be , or .
Either way, on any interval that does not include the value , the function can be restated as a linear function, which must have an inverse on that domain.
On the one interval that does contain this value, , two values can be found such that . For example,
is the correct response.
Example Question #65 : Functions/Series
Define function as follows:
has an inverse on each of the following domains except:
None of the other response gives a correct answer.
None of the other response gives a correct answer.
has an inverse on a given domain if and only if there are no two distinct values on the domain such that .
is a constantly increasing function, since it the equation of a line with positive slope. The cube root of a constantly increasing function is also constantly increasing, so
always increases as increases.
Therefore, if , . has an inverse on and, subsequently, any domain.