elements of calculus
posted by tara .
if d^2y/dx^2= x/x^2 +1, find d^4y/dx^4

d"=x/u where u = x^2+1
d"'= 1/u  x/u^2 * du/dx
d""= 1/u^2 1/u^2 du/dx +2x/u^3 (du/dx)^2 x/u^2 d"u/dx"
so now it is the algebra
du/dx= 2x
d"u/dx"= 2
go for it. check my work.