Hello, the following fraction is the derivative of a function:(adsbygoogle = window.adsbygoogle || []).push({});

(160-40t^2) / (t^2+4)^2

According to my textbook they have established the inflection points by equating the top line of this derived fraction to zero and then solving for x e.g. 160-40t^2 = 0. (t=+-2).

I was wondering is it a rule that you can simply equate the top line of a fraction format derivative to zero or am I missing something particular to this equation ?

Thanks for any clarification.

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# Establishing inflection point

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