Differential Equations

If \(m\) and \(n\) are order and degree of the question \(\left(\frac{d^2 y}{d x^2}\right)^4+8 \frac{\left(d^2 y / d x^2\right)^3}{\left(d^4 y / d x^4\right)^5}+\left(\frac{d^4 y}{d x^4}\right)=x^2+4\), then \(m-n\) is equal to