document.write( "Question 71928: If f(x)=x(x+1)(x-4), use interval notation to give all values of x where f(x)>0.\r
\n" ); document.write( "\n" ); document.write( "Help \n" ); document.write( "

Algebra.Com's Answer #51408 by stanbon(75887) $\"\"$ $\"About$

You can put this solution on YOUR website!
If f(x)=x(x+1)(x-4), use interval notation to give all values of x where f(x)>0.
\n" ); document.write( "f(x) is zero if x=0 or x=-1 or x=4
\n" ); document.write( "Mark those values on a number line.
\n" ); document.write( "Those three numbers result in four intervals on the number line.
\n" ); document.write( "Find the intervals where f(x) is positive or >0 by picking a test value
\n" ); document.write( "and substituting that for x in f(x). Note only the sign of the answer.
\n" ); document.write( "----------
\n" ); document.write( "Interval (-inf,-1): Pick x=-100; you get f(-100)= -*-*- which is <0
\n" ); document.write( "Interval (-1,0) : Pick x=-1/2; you get f(-1/2)= -*+*- which is >0
\n" ); document.write( "Interval (0,4) : Pick x=2 ; you get f(2) = +*+*_ which is <0
\n" ); document.write( "Interval (4,inf) : Pick x=100 ; you get f(100)= +*+*+ which is >0
\n" ); document.write( "---------
\n" ); document.write( "So the solution is: (-1,0) or (4,inf)
\n" ); document.write( "---------
\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "

\n" );