Find y' ?? please help

2 Answers
Feb 14, 2018

y'=[24x^5 e^[2y]-8x]/[1-8x^6e^[2y]]

Explanation:

sqrt[4x^2+y].... =4x^6e^[2y] squaring both sides will give
4x^2+y= 4x^6e^[2y]........Differentiating both sides
implicitly with respect x and using the product rule on the right hand side, i.e, d[uv]=vdu+udv

Let u =4x^6 and v=e^[2y]

8x+dy/dx=e^[2y]d/dx4x^6+4x^6d/dxe^[2y]

So , 8x+dy/dx=e^[2y]24x^5+4x^6e^[2y].2dy/dx ,rearranging and factoring........

dy/dx-8x^6e^[2y]dy/dx=24x^5e^[2y]-8x

dy/dx[1-8x^6e^[2y]]=24x^5e^[2y]-8x and so,

y'=[24x^5e^[2y]-8x]/[1-8x^6e^[2y]

Feb 14, 2018

dy/dx = ( 24x^5e^2y -8x) / ( 1- 8x^6e^(2y) )

Explanation:

We have:

sqrt(4x^2+y) = 2x^3e^y

If we have a function F(x, y) = 0 which defines y as a function of x, y = y(x), then:

dy/dx = − F_x / F_y

So Let F(x,y) = sqrt(4x^2+y)-2x^3e^y ; Then;

Then:

F_x = (partial F)/(partial x)

\ \ \ \ = 1/2(4x^2+y)^(-1/2)(8x)-6x^2e^y

\ \ \ \ = (4x)/sqrt(4x^2+y)-6x^2e^y

And:

F_y = (partial F)/(partial y)

\ \ \ \ = 1/2(4x^2+y)^(-1/2)(1)-2x^3e^y

\ \ \ \ = 1/(2sqrt(4x^2+y))-2x^3e^y

And so we have:

dy/dx = − F_x / F_y

\ \ \ \ \ = − ((4x)/sqrt(4x^2+y)-6x^2e^y) / (1/(2sqrt(4x^2+y))-2x^3e^y)

Using the original definition:

sqrt(4x^2+y) = 2x^3e^y

We can simplify our expression:

dy/dx = − ((4x)/(2x^3e^y)-6x^2e^y) / (1/(2(2x^3e^y))-2x^3e^y)

\ \ \ \ \ = − ( ( 4x -6x^2e^y(2x^3e^y) ) / (2x^3e^y) ) / ( ( 1-2x^3e^y(2)(2x^3e^y) ) / ((2)(2x^3e^y) )

\ \ \ \ \ = −2 ( 4x -6x^2e^y(2x^3e^y) ) / ( 1-2x^3e^y(4x^3e^y) )

\ \ \ \ \ = ( 24x^5e^2y -8x) / ( 1- 8x^6e^(2y) )