From the following equation, form a differential equation representing the given family of curves by eliminating arbitrary constants a and b.
y2=a(b2−x2)
Given family is y2=a(b2−x2). ....(i)
On differentiating w.r.t. x, we get
2yy′=a(0−2x)⇒2yy′=a(−2x)⇒yy′=−ax .....(ii)
Again differentiating w.r.t. x, we get
yy′′+(y′)2=−a (using product rule of differentiation) .....(iii)
Now, for eleminating a, put the value of a Eq. (iii) in Eq. (ii), we get
yy′=[yy′′+(y′)2]x⇒yy′=x[(y′)2+yy′]
which is the required differential equation.