Question 1028504
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When the denominator is zero:
{{{(8x^2-16x)/(5x^2-20)}}}
{{{5x^2-20=0}}}
{{{5x^2=20}}}
{{{x^2=4}}}
{{{x=sqrt(4)}}}
{{{x=2}}} {{{OR}}} {{{x=-2}}}
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I am unsure what a "hole" means, but if that is the term your instructor used,
the graph is not continuous at 2 and -2.
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{{{ graph( 500, 500, -3, 3, -3, 3, 5x^2-20) }}}  
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The graph should actually show a gap at 2 and -2, which is not clear in rendering.
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Sorry, best I can do .... Mac