Question $2$

Differentiate $f(u)=0\mathrm{.}07u^4-1\mathrm{.}21u^{3}3u-$

$f^{\text{'}}(u)=2\mathrm{.}8u^3-3\mathrm{.}63u^{2}3$

$f^{\text{'}}(u)=4u^3-3u^{2}3$

$f^{\text{'}}(u)=\mathrm{.}4u^3-3u^{2}3$

$f^{\text{'}}(u)=\mathrm{.}28u^3-3\mathrm{.}63u^{2}3$