GRE Math : Equations / Inequalities

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : Equations / Inequalities

\(\displaystyle y = 32\)

\(\displaystyle y = x^2 - 4\)

Quantity A: \(\displaystyle \frac{y}{7}\)

 

Quantity B: \(\displaystyle x\)

Possible Answers:

The two quantities are equal.

Quantity B is greater.

The relationship cannot be determined from the information given.

Quantity A is greater.

Correct answer:

The relationship cannot be determined from the information given.

Explanation:

We are given that y = 32.  Plug this value of y into the second equation.

32 = x2 – 4

36 = x2

x = +/– 6.

Next find a value for Quantity A:

y/7 = 32/7

This number is less than +6, but more than –6. Thus, the relationship cannot be determined from the information given.

Example Question #1 : Equations / Inequalities

Column A: \(\displaystyle \left | x \right |\)                             

Column B: \(\displaystyle x^3\)

 

Possible Answers:

The relationship cannot be determined.

Column B is greater.

Column A is greater.

The values are equal.

Correct answer:

The relationship cannot be determined.

Explanation:

Column B is greater for positive numbers.

The columns are equal for 0.

Column A is greater for negative numbers.

Because our answer changes depending on the value inserted, we cannot determine the relationship.

Example Question #1 : How To Find Out When An Equation Has No Solution

Find the solution to the following equation if x = 3: 

y = (4x2 - 2)/(9 - x2)

Possible Answers:

3

0

no possible solution

6

Correct answer:

no possible solution

Explanation:

Substituting 3 in for x, you will get 0 in the denominator of the fraction. It is not possible to have 0 be the denominator for a fraction so there is no possible solution to this equation.

Example Question #2 : Equations / Inequalities

Undefined_denom3

 

I.  x = 0

II. x = –1

III. x = 1

Possible Answers:

II and III only

I, II, and III

II only

I only

III only

Correct answer:

I only

Explanation:

 Undefined_denom2

Example Question #3 : Linear / Rational / Variable Equations

Nosol1

Possible Answers:

–3

1

There is no solution

–1/2

3

Correct answer:

There is no solution

Explanation:

Nosol2

Example Question #3 : Equations / Inequalities

\(\displaystyle \small h\left ( x\right )=\frac{28}{x+4}\)  

\(\displaystyle \small \textup{For which of the following values of}\,x\,\textup{is the above function undefined?}\)

Possible Answers:

None of the other answers

\(\displaystyle \small 4\)

\(\displaystyle \small -4\)

\(\displaystyle \small 28\)

\(\displaystyle \small 0\)

Correct answer:

\(\displaystyle \small -4\)

Explanation:

A fraction is considered undefined when the denominator equals 0. Set the denominator equal to zero and solve for the variable.

\(\displaystyle \small x+4=0\)

\(\displaystyle \small x=-4\)

Example Question #2 : How To Find Out When An Equation Has No Solution

Solve: 

\(\displaystyle 3(2x - 6) + 2x = 7x - 12\)

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle -30\)

\(\displaystyle 10\)

\(\displaystyle 30\)

\(\displaystyle -6\)

Correct answer:

\(\displaystyle 6\)

Explanation:

First, distribute, making sure to watch for negatives. 

\(\displaystyle 3(2x - 6) + 2x = 7x - 12\)

\(\displaystyle 6x - 18 + 2x = 7x - 12\)

Combine like terms. 

\(\displaystyle 8x - 18 = 7x - 12\)

Subtract 7x from both sides. 

\(\displaystyle x - 18 = -12\)

Add 18 on both sides and be careful adding integers. 

\(\displaystyle x = 6\)

Example Question #5 : Linear / Rational / Variable Equations

Solve: 

\(\displaystyle -3(2x - 5) = 9 - 6x\)

Possible Answers:

\(\displaystyle 15\)

\(\displaystyle \frac{15}{9}\)

Infinitely Many Solutions 

No Solution 

\(\displaystyle 9\)

Correct answer:

No Solution 

Explanation:

First, distribute the \(\displaystyle -3\) to the terms inside the parentheses.

\(\displaystyle -3(2x - 5) = 9 - 6x\)

\(\displaystyle -6x + 15 = 9 - 6x\)

Add 6x to both sides. 

\(\displaystyle 15 = 9\)

This is false for any value of \(\displaystyle x\). Thus, there is no solution. 

Example Question #1 : Linear / Rational / Variable Equations

Solve \(\displaystyle \left | 3-4x\right |< 0\).

Possible Answers:

No solutions

\(\displaystyle x< \frac{3}{4}\)

\(\displaystyle x< \frac{4}{3}\)

\(\displaystyle x>\frac{3}{4}\)

\(\displaystyle x>\frac{4}{3}\)

Correct answer:

No solutions

Explanation:

By definition, the absolute value of an expression can never be less than 0. Therefore, there are no solutions to the above expression.

Example Question #4 : Equations / Inequalities

\(\displaystyle (a+b)^2 =34\)

\(\displaystyle \frac{ab}{2}=6\)

Quantity A: \(\displaystyle a^2+b^2\)

Quantity B: 11

Possible Answers:

Quantity B is greater

The relationship cannot be determined.

The two quantities are equal.

Quantity A is greater

Correct answer:

Quantity B is greater

Explanation:

Expand \(\displaystyle (a+b)^2\) out into \(\displaystyle a^2+2ab+b^2\).

Since \(\displaystyle \frac{ab}{2}=6\), it can be seen that \(\displaystyle 2ab=24\)

\(\displaystyle (a+b)^2 =34\)

\(\displaystyle a^2+b^2+24=34\)

\(\displaystyle a^2+b^2=10\)

\(\displaystyle 10< 11\) so Quantity B is greater.

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