All GMAT Math Resources
Example Questions
Example Question #13 : Understanding Absolute Value
Define an operation as follows:
For all real numbers ,
Evaluate:
Example Question #12 : Absolute Value
Define an operation as follows:
For all real numbers ,
Evaluate
Example Question #445 : Algebra
Define an operation as follows:
For all real numbers ,
Evaluate
Example Question #14 : Understanding Absolute Value
Define a function to be
Give the range of the function.
An absolute value of a number must always assume a nonnegative value, so
, and
Therefore,
and the range of is the set .
Example Question #12 : Absolute Value
Solve the following equation:
Before we apply the absolute value to the two terms in the equation, we simplify what's inside of them first:
Now we can apply the absolute value to each term. Remember that taking the absolute value of a quantity results in solely its value, regardless of what its sign was before the absolute value was taken. This means that that absolute value of a number is always positive:
Example Question #12 : Absolute Value
Give the range of the function
The key to answering this question is to note that this equation can be rewritten in piecewise fashion.
If , since both and are nonnegative, we can rewrite as
, or
.
On , this has as its graph a line with positive slope, so it is an increasing function. The range of this part of the function is , or, since
,
.
If , since is negative and is positive, we can rewrite as
, or
is a constant function on this interval and its range is .
If , since both and are nonpositive, we can rewrite as
, or
.
On , this has as its graph a line with negative slope, so it is a decreasing function. The range of this part of the function is , or, since
, .
The union of the ranges is the range of the function - .
Example Question #12 : Absolute Value
Give the range of the function
None of the other choices gives a correct answer.
None of the other choices gives a correct answer.
The key to answering this question is to note that this equation can be rewritten in piecewise fashion.
If , since both and are positive, we can rewrite as
, or
,
a constant function with range .
If , since is negative and is positive, we can rewrite as
, or
This is decreasing, as its graph is a line with negative slope. The range is ,
or, since
and
,
.
If , since both and are negative, we can rewrite as
, or
,
a constant function with range .
The union of the ranges is the range of the function - - which is not among the choices.
Example Question #21 : Understanding Absolute Value
Simplify the following expression:
This question plays a few tricks dealing with absolute values. To begin, we can recognize that any negative sign within an absolute value can basically be rendered positive. So this:
becomes:
In this case, we still have a negative that was outside of the absolute value sign. This term will stay negative, so we get:
This makes our answer .
Example Question #21 : Absolute Value
Solve the following inequality:
To solve this absolute value inequality, we must remember that the absolute value of a function that is less than a certain number must be greater than the negative of that number. Using this knowledge, we write the inequality as follows, and then perform some algebra to solve for :
Example Question #22 : Understanding Absolute Value
Solve the following inequality:
or
or
or
or
To solve this absolute value inequality, we must remember that the absolute value of a function that is greater than a certain number is also less than the negative of that number. With this in mind, we rewrite the inequality as follows and then solve for the possible intervals of :
or
or
or