Question 990509
Use implicit differentiation,
{{{3x^2dx+4(xdy+ydx)-2ydy=0}}}
{{{3x^2dx+4xdy+4ydx-2ydy=0}}}
{{{(4x-2y)dy=-(3x^2+4y)dx}}}
{{{dy/dx=-((3x^2+4y)/(4x-2y))}}}
So when {{{x=2}}} and {{{y=1}}},
{{{dy/dx=-((3(2)^2+4(1))/(4(2)-2(1)))}}}
{{{dy/dx=-((12+4)/(8-2))}}}
{{{dy/dx=-(16/6)}}}
{{{dy/dx=-(8/3)}}}
.
.
.
*[illustration fd25.JPG].