document.write( "Question 1199000: Solve for x the inequality equation (x+9)/(x+1) -2 > 0\r
\n" ); document.write( "\n" ); document.write( "The correct answer is one of the following. Which one is correct?\r
\n" ); document.write( "\n" ); document.write( "A) -1 < x < 7\r
\n" ); document.write( "\n" ); document.write( "B) x > 7\r
\n" ); document.write( "\n" ); document.write( "C) -1 < x < 8\r
\n" ); document.write( "\n" ); document.write( "D) x > 8
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Algebra.Com's Answer #832692 by math_tutor2020(3817)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "As the tutor @greenestamps has shown
\n" ); document.write( "\"%28x%2B9%29%2F%28x%2B1%29+-2+%3E+0\"
\n" ); document.write( "simplifies to
\n" ); document.write( "\"%28-x%2B7%29%2F%28x%2B1%29+%3E+0\"\r
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\n" ); document.write( "\n" ); document.write( "If x = 7, then the numerator is 0.
\n" ); document.write( "If x = -1, then the denominator is 0, so we must avoid this x value.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Draw a number line with -1 and 7 marked on it.
\n" ); document.write( "Label the following regions or intervals
\n" ); document.write( "P: -infinity < x < -1
\n" ); document.write( "Q: -1 < x < 7
\n" ); document.write( "R: 7 < x < infinity
\n" ); document.write( "
\n" ); document.write( "Note the open holes at -1 and 7.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Let's select an x value from interval P (shown in red above)
\n" ); document.write( "I'll pick x = -2
\n" ); document.write( "\"%28-x%2B7%29%2F%28x%2B1%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%28-%28-2%29%2B7%29%2F%28-2%2B1%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%289%29%2F%28-1%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"-9+%3E+0\"
\n" ); document.write( "which is false, so x = -2 is not a solution to the inequality.
\n" ); document.write( "By extension any item in interval P will also be non-solutions.
\n" ); document.write( "This rules out interval P from the solution set.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now pick something from interval Q.
\n" ); document.write( "I'll go for x = 0
\n" ); document.write( "\"%28-x%2B7%29%2F%28x%2B1%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%28-0%2B7%29%2F%280%2B1%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%287%29%2F%281%29+%3E+0\"\r
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\n" ); document.write( "\n" ); document.write( "\"7+%3E+0\"
\n" ); document.write( "which is true.
\n" ); document.write( "You should find similar true results for any other value in interval Q.
\n" ); document.write( "So interval Q is part of the answer.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Lastly, we need to check interval R.
\n" ); document.write( "Let's say we select x = 8
\n" ); document.write( "\"%28-x%2B7%29%2F%28x%2B1%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%28-8%2B7%29%2F%288%2B1%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%28-1%29%2F%289%29+%3E+0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"-0.111+%3E+0\" approximately
\n" ); document.write( "Like with interval P, we get a false statement
\n" ); document.write( "So anything in interval R leads to a false statement.\r
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\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Therefore, the only valid solution set is -1 < x < 7
\n" ); document.write( "Which in interval notation would be (-1,7)
\n" ); document.write( "Be sure not to mix this up with ordered pair notation.\r
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\n" ); document.write( "\n" ); document.write( "Confirmation can be done using a graph.
\n" ); document.write( "Desmos or GeoGebra are good free graphing tools.
\n" ); document.write( "
\n" ); document.write( "The green curve represents y = (x+9)/(x+1) -2 aka y = (-x+7)/(x+1)
\n" ); document.write( "This green curve is above the x axis on the interval -1 < x < 7
\n" ); document.write( "It is below the x axis when either x < -1 or when x > 7.
\n" ); document.write( "The x intercept is 7, and there's a vertical asymptote at x = -1.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "-------------------------------------------------------\r
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\n" ); document.write( "\n" ); document.write( "Answer: Choice A) -1 < x < 7
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