The radius of a circular ink spot, t seconds after it first appears, is given by:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]r=\frac{1+4t}{2+t}[/tex]

Find the rate of increase (in cm/s) at the time when th radius as doubled from its initial value.

I have attached my working; however, the answer is7/9cm/sand I keep getting 9/7cm/s. Does that even make sense if it is doubling anyways?

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# Homework Help: Rate of Increase Question

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