[tex]\bf y=t\left[ ln(7t) \right]^2\impliedby \textit{product rule}\\\\
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\cfrac{dy}{dt}=1\cdot \left[ ln(7t) \right]^2+t\cdot 2\left[ ln(7t) \right]\cdot \left( \cfrac{7}{7t} \right)\cdot 7\impliedby chain-rule
\\\\\\
\cfrac{dy}{dt}=\left[ ln(7t) \right]^2+ln(7t)\cdot 2t\cdot \cfrac{1}{t}\cdot 7\implies \cfrac{dy}{dt}=\left[ ln(7t) \right]^2+14ln(7t)[/tex]
