Question 397931: Find the intervals where the graph of the function f(x)=x^2-4 is above the x-axis.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Find the intervals where the graph of
the function f(x)=x^2-4 is above the x-axis.
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Since the coefficient of x^2 is positive,
the parabola opens up.
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Since x^2-4 = (x-2)(x+2) = 0 means
the x-intercepts are x=-2 and x=+2.
The vertex is inbetween -2 and +2
and is below the x-axis.
So f(x) is positive in these
intervals: (-inf,-2)U(2,+inf)
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Cheers,
Stan H.
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