19 $y'$=$(4x^2+2x)'$(3x-$7x^5$)+$(3x-7x^5)'.$(4x^2+2x)$
$y'$=(8x+2)$(3x-7x^5)$+$(3-35x^4)$($4x^2$+2x)
$y'$=$24x^2-56x^6+6x-14x^5+12x^2+6x-140x^6-70x^5$
$y'$=$36x^2-196x^6+12-84x^5$
=> 36-196+12-84=-232
20 $y'$=(x+1)'$\sqrt[]{x^2+x+1}$ +($\sqrt[]{x^2+x+1}$ )'(x+1)
$y'$=$\sqrt[]{x^2+x+1}+\dfrac{(2x+1)(x+1)}{2\sqrt[]{x^2+x+1} } $
$y'$=$\dfrac{2x^2+2x+2+2x^2+3x+1}{2 \sqrt[]{x^2+x+1}}$
$y'$=$\dfrac{4x^2+5x+3}{2\sqrt[]{x^2+x+1} }$
xin hay nhất
