



 
Hi Christy, I agree with your differentiation. If $s(t) = (t  6)^4 (t + 1)^2$ then \[s'(t) = 4(t  6)^3 (t + 1)^2 + 2(t + 1) (t  6)^4 .\] This expression has two terms $4(t  6)^3 (t + 1)^2 \mbox{ and } 2(t + 1) (t  6)^4$ and these terms have common factors, $2, (t  6)^3$ and $(t + 1).$ Hence the derivative $s'(t)$ can be written as \[s'(t) = 2 (t  6)^3 (t + 1)[2(t + 1) + (t  6)].\] Can you proceed from here? Penny  


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