2024/G3/12

$\color {Purple}Product\,Rule$
${\frac {d}{dx}}[f\cdot {g}]={\frac {d}{dx}}[f]\cdot {g}+{\frac {d}{dx}}[g]\cdot {f}$
$\color {Blue}Quotient\,Rule$
${\frac {d}{dx}}[{\frac {f}{g}}]={\frac {{\frac {d}{dx}}[f]\cdot {g}-{\frac {d}{dx}}[g]\cdot {f}}{g^{2}}}$
$\mathbf {\color {Purple}{Examples}}$
$\mathbf {Ex.1}$
$if\,f(x)=x\cdot {e^{x}}$
$f^{\prime }(x)=1\cdot {e^{x}}+x\cdot {e^{x}}$
$\mathbf {Ex.2}$
$if\,f(t)={\sqrt {t}}(a+bt)$
$f^{\prime }(t)={\frac {1}{2{\sqrt {t}}}}(a+bt)+t{\sqrt {t}}(b)$
$\mathbf {Ex.3}$
$if\,f(x)={\sqrt {x}}\cdot {g(x)}$
$g(4)=2$
$g^{\prime }(4)=3$
$f^{\prime }(x)={\frac {1}{2{\sqrt {x}}}}\cdot {g(x)}+{\sqrt {x}}\cdot {g^{\prime }(x)}$
$\mathbf {Ex.4}$
$y={\frac {\color {Blue}{x^{2}+x-2}}{\color {Red}{x^{3}+6}}}$
${\frac {d}{dx}}=y^{\prime }={\frac {(2x+1)(x^{3}-6)-\color {Blue}{(x^{2}+x-2)}(3x^{2})}{\color {Red}{(x^{3}+6)^{2}}}}$
$={\frac {(2x^{4}+x^{4}+x^{3}+12x+6-[3x^{4}+3x^{2}-6x^{2}]}{(x^{3}+6)^{2}}}$
$={\frac {-x^{4}-2x^{3}+6x^{2}+12x+6}{(x^{3}+6)^{2}}}$
$\mathbf {Ex.5}$
$y={\frac {e^{x}}{1+x^{2}}}\,(1,{\frac {e}{2}})\,$
${\frac {d}{dx}}={\frac {e^{x}\cdot (1+x^{2})-e^{x}(2x)}{(1+x^{2})^{2}}}$
${\frac {d}{dx}}|_{x=1}{\frac {e(1+1)-e^{\prime }(2)}{(1+1)^{2}}}={\frac {2e-2e}{2^{2}}}={\frac {0}{4}}=0$