document.write( "Question 174989: the inequality x^2-2x<8 is equivalent to what? \n" ); document.write( "
Algebra.Com's Answer #130055 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
\"x%5E2-2x%3C8\" Start with the given inequality.\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2-2x-8%3C0\" Subtract 8 from both sides.\r
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\n" ); document.write( "\n" ); document.write( "\"%28x%2B2%29%28x-4%29%3C0\" Factor the left side\r
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\n" ); document.write( "\n" ); document.write( "\"%28x%2B2%29%28x-4%29=0\" Set the left side equal to zero\r
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\n" ); document.write( "\n" ); document.write( "Set each individual factor equal to zero:\r
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\n" ); document.write( "\n" ); document.write( "\"x%2B2=0\" or \"x-4=0\" \r
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\n" ); document.write( "\n" ); document.write( "Solve for x in each case:\r
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\n" ); document.write( "\n" ); document.write( "\"x=-2\" or \"x=4\" \r
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\n" ); document.write( "\n" ); document.write( "So our critical values are \"x=-2\" and \"x=4\" \r
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\n" ); document.write( "\n" ); document.write( "Now set up a number line and plot the critical values on the number line\r
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\n" ); document.write( "\n" ); document.write( "\"number_line%28+600%2C+-10%2C+10%2C-2%2C4%29\"\r
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\n" ); document.write( "\n" ); document.write( "So let's pick some test points that are near the critical values and evaluate them.\r
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\n" ); document.write( "\n" ); document.write( "Let's pick a test value that is less than \"-2\" (notice how it's to the left of the leftmost endpoint):\r
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\n" ); document.write( "\n" ); document.write( "So let's pick \"x=-3\"\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2-2x-8%3C0\" Start with the given inequality\r
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\n" ); document.write( "\n" ); document.write( "\"%28-3%2B2%29%28-3-4%29%3C+0\" Plug in \"x=-3\"\r
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\n" ); document.write( "\n" ); document.write( "\"7%3C+0\" Evaluate and simplify the left side\r
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\n" ); document.write( "\n" ); document.write( "Since the inequality is false, this means that the interval does not work. So this interval is not in our solution set and we can ignore it.\r
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\n" ); document.write( "\n" ); document.write( "Let's pick a test value that is in between \"-2\" and \"4\":\r
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\n" ); document.write( "\n" ); document.write( "So let's pick \"x=1\"\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2-2x-8%3C0\" Start with the given inequality\r
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\n" ); document.write( "\n" ); document.write( "\"%281%2B2%29%281-4%29%3C+0\" Plug in \"x=1\"\r
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\n" ); document.write( "\n" ); document.write( "\"-9%3C+0\" Evaluate and simplify the left side\r
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\n" ); document.write( "\n" ); document.write( "Since the inequality is true, this means that the interval works. So this tells us that this interval is in our solution set.\r
\n" ); document.write( "\n" ); document.write( " So part our solution in interval notation is ()\r
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\n" ); document.write( "\n" ); document.write( "Let's pick a test value that is greater than \"4\" (notice how it's to the right of the rightmost endpoint):\r
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\n" ); document.write( "\n" ); document.write( "So let's pick \"x=5\"\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2-2x-8%3C0\" Start with the given inequality\r
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\n" ); document.write( "\n" ); document.write( "\"%285%2B2%29%285-4%29%3C+0\" Plug in \"x=5\"\r
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\n" ); document.write( "\n" ); document.write( "\"7%3C+0\" Evaluate and simplify the left side\r
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\n" ); document.write( "\n" ); document.write( "Since the inequality is false, this means that the interval does not work. So this interval is not in our solution set and we can ignore it.\r
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\n" ); document.write( "\n" ); document.write( "Summary:\r
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\n" ); document.write( "\n" ); document.write( "So the solution set is \r
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\n" ); document.write( "\n" ); document.write( "So the solution in interval notation is:\r
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\n" ); document.write( "\n" ); document.write( "()\r
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