Write the sum of the order and degree of the following differential equation: ddx(dydx)³=0

By using chain rule to evaluate the derivative on the left hand side, we get:
ddx(dydx)³=0.⇒3(dydx)²d²ydx²=0
The order of this differential equation is 2 because the highest order derivative appearing in the equation is second order.
The degree is the power of this highest order derivative. In this case degree is 1.
So, the answer is 2+1=3.