The given equation is $- 5 x^{2} - 4 y^{2}{\left(x \right)} + y{\left(x \right)} \cos{\left(x \right)}=0$.
Step 2: Differentiate both sides of the equation with respect to x
The differentiation result is $- 10 x - y{\left(x \right)} \sin{\left(x \right)} - 8 y{\left(x \right)} \frac{d}{d x} y{\left(x \right)} + \cos{\left(x \right)} \frac{d}{d x} y{\left(x \right)}=0$.
Step 3: Rearrange the resulting equation to solve for dy/dx
Rearranging gives $\frac{10 x + y{\left(x \right)} \sin{\left(x \right)}}{- 8 y{\left(x \right)} + \cos{\left(x \right)}}$ as the expression for $\frac{dy}{dx}$.
Final Answer:
The derivative of $y$ with respect to $x$ is $\frac{dy}{dx} = \frac{10 x + y{\left(x \right)} \sin{\left(x \right)}}{- 8 y{\left(x \right)} + \cos{\left(x \right)}}$.