College Algebra : Linear Inequalities

Study concepts, example questions & explanations for College Algebra

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Example Questions

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Example Question #61 : Solving Equations And Inequallities

Express the following linear inequality in interval notation.

Possible Answers:

Correct answer:

Explanation:

Upon solving for x, we find that 6 is less than x which is less than 7, or that x is greater than 6 AND x is less than 7.  The left-hand term of our interval is 6 since it is the lower bound for our set, and there is a parenthesis around it since it is not in our set (6 is not greater than 6).  The right-hand term of our interval is 7 since it is the upper bound for our set, and there is a parenthesis around it since it is not in our set (7 is not less than 7). Remember to flip the direction of the inequalities when dividing or multiplying by a negative number.

Example Question #11 : Linear Inequalities

Express the following linear inequality in interval notation.

Possible Answers:

Correct answer:

Explanation:

Upon solving for x, we find that x is greater than or equal to 10/3.  The left-hand term of the interval is 10/3 since it is the lower bound of our set, and there is a bracket around it because it is in our set (10/3 is greater than or equal to 10/3).  The right-hand term of the interval is infinity since any number larger than 10/3 is in our set, and there is always parenthesis around infinity.

Example Question #11 : Linear Inequalities

Marvin's Movers charges $100 plus $30 per hour to move a household across town.  Elliot's Moving Service charges $55 per hour.  For what lengths of time does it cost less to hire Marvin's Movers?

Possible Answers:

More than 4 hours

More than 6 hours

Less than 4 hours

More than 5 hours 

Less than 5 hours

Correct answer:

More than 4 hours

Explanation:

Our variable x represents the number of hours to move.  Marvin's rate can be expressed as 30x+100.  Elliot's rate can be expressed as 55x.  We must set the expression for Marvin's rate less than Elliot's rate: .  Upon solving for x, we find that x is greater than 4, so Marvin's is cheaper for jobs greater than 4 hours.

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