$(("d"^2y)/("d"x^2))^3 = sqrt(1 + (("d"y)/("d"x)))$
On squaring both sides, we get
$(("d"^2y)/("d"x^2))^(3 xx 2) = 1 + (("d"y)/("d"x))$
$(("d"^2y)/("d"x^2))^6 = 1 + ("d"y)/("d"x)$
In this equation
The highest order derivative is $("d"^2y)/("d"x^2)$ and its power is 6.
Its order = 2 and degree = 6