GRE Subject Test: Math : Classifying Algebraic Functions

Study concepts, example questions & explanations for GRE Subject Test: Math

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Example Questions

Example Question #1 : Absolute Value Inequalities

\(\displaystyle 5\left | x-7\right |+14< 39\)

Possible Answers:

\(\displaystyle x< 12\)

\(\displaystyle 2< x< 12\)

\(\displaystyle x> 12\) or \(\displaystyle x< 2\)

\(\displaystyle 2< x\)

Correct answer:

\(\displaystyle 2< x< 12\)

Explanation:

The first thing we must do is get the absolute value alone: \(\displaystyle 5\left | x-7\right |+14< 39\)

\(\displaystyle 5\left | x-7\right |< 25\)

\(\displaystyle \left | x-7\right |< 5\)

When we're working with absolute values, we are actually solving two equations:

\(\displaystyle x-7< 5\)     and \(\displaystyle x-7> -5\)

Fortunately, these can be written as one equation:

\(\displaystyle -5< x-7< 5\)

If you feel more comfortable solving the equations separately then go ahead and do so.

\(\displaystyle 2< x< 12\)

              To get \(\displaystyle x\) alone, we added \(\displaystyle 7\) on both sides of the inequality sign

 

Example Question #2 : Absolute Value Inequalities

\(\displaystyle \left | y\right | + 18 \leq 11.3\)

Possible Answers:

There is no solution.

\(\displaystyle y\geq 6.7\)

\(\displaystyle y\leq 29.3\)

\(\displaystyle y\leq -6.7\)

Correct answer:

There is no solution.

Explanation:

\(\displaystyle \left | y\right | + 18 \leq 11.3\)

\(\displaystyle \left | y\right |\leq -6.7\)

Because Absolute Value must be a non-negative number, there is no solution to this Absolute Value inequality.

Example Question #1 : Absolute Value Inequalities

The weight of the bowling balls manufactured at the factory must be \(\displaystyle 8\) lbs. with a tolerance of \(\displaystyle 3\) lbs.  Which of the following absolute value inequalities can be used to assess which bowling balls are tolerable?

Possible Answers:

\(\displaystyle \left | w-8\right | \leq 3\)

\(\displaystyle \left | w-8\right | \geq 3\)

\(\displaystyle \left | w-3 \right | \leq 8\)

\(\displaystyle \left | w-3 \right |\geq 8\)

Correct answer:

\(\displaystyle \left | w-8\right | \geq 3\)

Explanation:

The following absolute value inequality can be used to assess the bowling balls that are tolerable:

\(\displaystyle \left | w-8\right |\geq3\)

Example Question #31 : Inequalities

\(\displaystyle 4\left |(x+0.3)\right | - 3 < 11\)

Possible Answers:

There is no solution.

\(\displaystyle x< 3.2\) and \(\displaystyle x> -2.3\)

\(\displaystyle x> 3.2\) and \(\displaystyle x< -2.3\)

\(\displaystyle x< -3.2\) and \(\displaystyle x> -2.3\)

Correct answer:

\(\displaystyle x< 3.2\) and \(\displaystyle x> -2.3\)

Explanation:

\(\displaystyle 4\left |(x+0.3) \right | - 3< 11\)

\(\displaystyle 4x + 1.2 - 3 < 11\)

\(\displaystyle 4x -1.8< 11\)

\(\displaystyle 4x -1.8 +1.8< 11 + 1.8\)

\(\displaystyle 4x< 12.8\)

\(\displaystyle \frac{4x}{4} < \frac{12.8}{4}\)

\(\displaystyle x< 3.2\)

 

\(\displaystyle 4x + 1.2 - 3> -11\)

\(\displaystyle 4x - 1.8> -11\)

\(\displaystyle 4x - 1.8 + 1.8> -11 + 1.8\)

\(\displaystyle 4x > -9.2\)

\(\displaystyle \frac{4x}{4}>\frac{-9.2}{4}\)

\(\displaystyle x> -2.3\)

 

The correct answer is \(\displaystyle x< 3.2\) and \(\displaystyle x>2.3\)

Example Question #2 : Absolute Value Inequalities

\(\displaystyle \left | 6+x\right |-4 < 0\)

Possible Answers:

\(\displaystyle x< 2\) and \(\displaystyle x>10\)

\(\displaystyle x>-2\) and \(\displaystyle x< -10\)

\(\displaystyle x< -2\) and \(\displaystyle x> -10\)

\(\displaystyle x< 2\) and \(\displaystyle x > 10\)

Correct answer:

\(\displaystyle x< -2\) and \(\displaystyle x> -10\)

Explanation:

\(\displaystyle \left | 6+x\right | -4 < 0\)

 

\(\displaystyle 6 + x -4 < 0\)

\(\displaystyle 6 + x < 4\)

\(\displaystyle 6-6 + x < 4-6\)

\(\displaystyle x< -2\)

 

 

\(\displaystyle 6 + x > -4\)

\(\displaystyle 6-6 + x > -6-4\)

\(\displaystyle x>-10\)

 

The correct answer is \(\displaystyle x< -2\) and \(\displaystyle x>-10.\)

 

 

 

 

Example Question #1 : Absolute Value Inequalities

\(\displaystyle \left | \frac{x-6}{2} \right |\leq 3\)

Possible Answers:

\(\displaystyle x\geq 0\)  and   \(\displaystyle x\leq 12\)

There is no solution.

  \(\displaystyle x\geq 0\)  and\(\displaystyle x\leq 12\)

\(\displaystyle x\leq 0\) and \(\displaystyle x\geq12\)

Correct answer:

  \(\displaystyle x\geq 0\)  and\(\displaystyle x\leq 12\)

Explanation:

\(\displaystyle \left | \frac{x-6}{2} \right |\leq3\)

\(\displaystyle \frac{2}{1} \left | \frac{x-6}{2} \right | \leq 2\times3\)

\(\displaystyle x-6 \leq 6\)

\(\displaystyle x\leq 12\)

 

\(\displaystyle \frac{2}{1} \left | \frac{x-6}{2} \right | \geq 2 \times -3\)

\(\displaystyle x-6 \geq -6\)

\(\displaystyle x\geq 0\)

The correct answer is \(\displaystyle x\leq12\)  and \(\displaystyle x\geq 0.\)

Example Question #31 : Inequalities

\(\displaystyle \left | x-5\right |\leq7\)

Possible Answers:

\(\displaystyle x\geq12\) and  \(\displaystyle x\leq -2\)

\(\displaystyle x\leq-12\) and \(\displaystyle x \geq 2\)

\(\displaystyle x< 12\) and \(\displaystyle x> -2\)

\(\displaystyle x\leq12\) and  \(\displaystyle x\geq-2\)

Correct answer:

\(\displaystyle x\leq12\) and  \(\displaystyle x\geq-2\)

Explanation:

\(\displaystyle \left | x-5\right |\leq 7\)

\(\displaystyle x-5 \leq 7\)

\(\displaystyle x-5 + 5 \leq 7 +5\)

\(\displaystyle x\leq 12\)

 

\(\displaystyle x-5 \geq -7\)

\(\displaystyle x-5 +5 \geq -7 +5\)

\(\displaystyle x\geq -2\)

 

The correct answer is \(\displaystyle x\leq12\) and \(\displaystyle x\geq -2.\)

Example Question #2 : Absolute Value Inequalities

A type of cell phone must be less than 9 ounces with a tolerance of 0.4 ounces. Which of the following inequalities can be used to assess which cell phones are tolerable? (w refers to the weight).

Possible Answers:

\(\displaystyle \left | w-9\right | \leq 0.4\)

\(\displaystyle \left | w-0.4\right | \leq 9\)

\(\displaystyle \left | w-0.4\right | \geq 9\)

\(\displaystyle \left | w-9\right | \geq 0.4\)

Correct answer:

\(\displaystyle \left | w-9\right | \leq 0.4\)

Explanation:

The Absolute Value Inequality that can assess which cell phones are tolerable is:

\(\displaystyle \left | w-0.4\right | \leq 9\)

Example Question #2 : Absolute Value Inequalities

Solve for x: \(\displaystyle |x-1|\le 5\)

Possible Answers:

\(\displaystyle x \le 6\)

\(\displaystyle x \ge 6\)

\(\displaystyle x < 6\)

\(\displaystyle x>6\)

Correct answer:

\(\displaystyle x \le 6\)

Explanation:

Step 1: Separate the equation into two equations:

First Equation: \(\displaystyle |x-1|\le 6\)
Second Equation: \(\displaystyle -(x-1)\ge -5\)

Step 2: Solve the first equation

\(\displaystyle x-1\le 5\)
\(\displaystyle x-1+1\le 5+1\)
\(\displaystyle x \le 6\)

Step 3: Solve the second equation

\(\displaystyle -(x+1)\ge -5\)
\(\displaystyle -x+1\ge -5\)
\(\displaystyle -x+1-1\ge -5-1\)

\(\displaystyle -x \ge -6\)

\(\displaystyle \rightarrow x \le 6\)

The solution is \(\displaystyle x\le 6\)

Example Question #1 : Absolute Value Inequalities

Which of the following expresses the entire solution set of \(\displaystyle \left | x-10\right |+ 3 < 12\)?

Possible Answers:

\(\displaystyle x< 1\) and \(\displaystyle x>19\)

\(\displaystyle x>19\) and \(\displaystyle x< -5\)

\(\displaystyle 1< x< 19\)

\(\displaystyle -5< x< 19\)

Correct answer:

\(\displaystyle 1< x< 19\)

Explanation:

Before expanding the quantity within absolute value brackets, it is best to simplify the "actual values" in the problem. Thus \(\displaystyle \left | x-10 \right |+3< 12\) becomes:

 

\(\displaystyle \left | x-10 \right |< 9\)

 

From there, note that the absolute value means that one of two things is true: \(\displaystyle x-10< 9\) or \(\displaystyle x-10>-9\). You can therefore solve for each possibility to get all possible solutions. Beginning with the first:

\(\displaystyle x-10< 9\) means that:

\(\displaystyle x< 19\)

 

For the second:

\(\displaystyle x-10>-9\) means that:

\(\displaystyle x>1\)

 

Note that the two solutions can be connected by putting the inequality signs in the same order:

 

\(\displaystyle 1< x< 19\)

 

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