SOLUTION: if f(x)=x(x+1)(x-4), use interval notation to give all values of x where f(x)>0

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Question 73727: if f(x)=x(x+1)(x-4), use interval notation to give all values of x where f(x)>0
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
If we look at the roots of x(x+1)(x-4) we get x=0, x=-1, and x=4. At the roots the graph of f(x) goes from either a positive number to a negative number or from a negative number to a positive number. At this point we only care about the positive portion. So if we graph x(x+1)(x-4) we get
graph%28+300%2C+200%2C+-3%2C+5%2C+-10%2C+10%2C+x%2A%28x%2B1%29%2A%28x-4%29%29+
So the roots are the endpoints where the interval is
[-1,0]U[4,infinity) Which can be easily obtained from the graph.