L7 Absolute Value and Rational Inequalities - Part 4
Unit 1A
Precalculus
Lesson 7: Absolute Value and Rational Inequalities
To eliminate the denominator, multiply both sides of the inequality by «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»x«/mi»«mo»§#8722;«/mo»«mn»5«/mn»«/mrow»«/mstyle»«/math».
Combine «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»x«/mi»«mo»§#62;«/mo»«mn»5«/mn»«/mrow»«/mstyle»«/math» with the solution «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»x«/mi»«mo»§#8804;«/mo»«mfrac»«mn»17«/mn»«mn»2«/mn»«/mfrac»«/mrow»«/mstyle»«/math». «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfenced close=¨]¨»«mrow»«mn»5«/mn»«mi mathvariant=¨normal¨»,«/mi»«mspace width=¨0.33em¨/»«mfrac»«mn»17«/mn»«mn»2«/mn»«/mfrac»«/mrow»«/mfenced»«/mstyle»«/math»
To eliminate the denominator, multiply both sides of the inequality by «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»x«/mi»«mo»§#8722;«/mo»«mn»5«/mn»«/mrow»«/mstyle»«/math».
Since «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»x«/mi»«mo»-«/mo»«mn»5«/mn»«/mrow»«/mstyle»«/math» is assumed to be a negative value, the inequality symbol reverses direction when it is multiplied by this negative value. |
Combine «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»x«/mi»«mo»§#60;«/mo»«mn»5«/mn»«/mrow»«/mstyle»«/math» with the solution «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»x«/mi»«mo»§#8805;«/mo»«mfrac»«mn»17«/mn»«mn»2«/mn»«/mfrac»«/mrow»«/mstyle»«/math». These combined results mean the solution is the set of all numbers less than «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mn»5«/mn»«/mstyle»«/math», but greater than or equal to «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfrac»«mn»17«/mn»«mn»2«/mn»«/mfrac»«/mstyle»«/math». Since this leads to a contradiction (there is no number that is both less than «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mn»5«/mn»«/mstyle»«/math», and greater than or equal to «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfrac»«mn»17«/mn»«mn»2«/mn»«/mfrac»«/mstyle»«/math»), this case does not yield a solution. The only solution is from Case 1.
Therefore, the solution to the inequality «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mfrac»«mrow»«mi»x«/mi»«mo»+«/mo»«mn»2«/mn»«/mrow»«mrow»«mi»x«/mi»«mo»§#8722;«/mo»«mn»5«/mn»«/mrow»«/mfrac»«mo»§#8805;«/mo»«mn»3«/mn»«/mrow»«/mstyle»«/math» is «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfenced close=¨]¨»«mrow»«mn»5«/mn»«mi mathvariant=¨normal¨»,«/mi»«mo»§#160;«/mo»«mfrac»«mn»17«/mn»«mn»2«/mn»«/mfrac»«/mrow»«/mfenced»«/mstyle»«/math». The graph of this solution is shown below.
Graphically, the solution is as follows. Graph the functions «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»y«/mi»«mo»=«/mo»«mfrac»«mrow»«mi»x«/mi»«mo»+«/mo»«mn»2«/mn»«/mrow»«mrow»«mi»x«/mi»«mo»§#8722;«/mo»«mn»5«/mn»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math» and «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»y«/mi»«mo»=«/mo»«mn»3«/mn»«/mrow»«/mstyle»«/math». Find the values of «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»x«/mi»«/mstyle»«/math» for which the graph «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»y«/mi»«mo»=«/mo»«mfrac»«mrow»«mi»x«/mi»«mo»+«/mo»«mn»2«/mn»«/mrow»«mrow»«mi»x«/mi»«mo»§#8722;«/mo»«mn»5«/mn»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math» lies on or above the line «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»y«/mi»«mo»=«/mo»«mn»3«/mn»«/mrow»«/mstyle»«/math».
