document.write( "Question 72717: I'm confused...help?\r
\n" ); document.write( "\n" ); document.write( "If f(x) = x(x + 1)(x - 4), use interval notation to give all values of x where f(x)>0. \n" ); document.write( "
Algebra.Com's Answer #52004 by stanbon(75887)\"\" \"About 
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If f(x) = x(x + 1)(x - 4), use interval notation
\n" ); document.write( "to give all values of x where f(x)>0.\r
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\n" ); document.write( "Find the values when f(x)=0
\n" ); document.write( "They are x=-1, or x=0, or x=4
\n" ); document.write( "Draw a number line and put the values -1,0,and 4 in proper order.
\n" ); document.write( "This determines 4 intervals; determines which intervals are part
\n" ); document.write( "of the solution set for f(x)>0 by choosing a test pt in each interval
\n" ); document.write( "and determining the sign of f(x)
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\n" ); document.write( "In (-inf,-1) choose x--100 where f(x)=-*-*- which is negative, so no solutions
\n" ); document.write( "In (-1,0) choose x=-1/2 where f(x)=-*+*- which is positive, so solutions here
\n" ); document.write( "In (0,4) choose x=2 where f(x)=+*+*- which is negative, so no solutions here
\n" ); document.write( "In (4,+inf) choose x=100 where f(x)=+*+*+ which is positive , so solutions here
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\n" ); document.write( "Therefore the solutions are in these intervals: (-1,0) union (4,+inf)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "
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