Differentiate y^2 = 4axy2=4ax w.r.t xx (Where a is a constant)?

1 Answer
Aug 2, 2017

dy/dx = (2a)/(y) dydx=2ay

Explanation:

When we differentiate yy wrt xx we get dy/dxdydx.

However, we only differentiate explicit functions of yy wrt xx. But if we apply the chain rule we can differentiate an implicit function of yy wrt yy but we must also multiply the result by dy/dxdydx.

Example:

d/dx(y^2) = d/dy(y^2)dy/dx = 2ydy/dx ddx(y2)=ddy(y2)dydx=2ydydx

When this is done in situ it is known as implicit differentiation.

Now, we have:

y^2=4ax \ \ \ , the equation of a Parabola in standard form

Implicitly differentiating wrt x

d/dx y^2 = d/dx 4ax

:. 2ydy/dx = 4a

:. dy/dx = (4a)/(2y)

:. dy/dx = (2a)/(y)