2udu/( 1-u^2) = dy/y
-ln( 1-u^2) = lny+lnC
Cy( 1-u^2) = 1
Y (0) = 1,P (0) = Y' (0) =- 1,U (0) = P (0)/Y (0) =- 1? C is infinite.
So only the constant function u = 1 and u(0) =-1 is satisfied, then u =-1.
p = -y,dy/dx = -y,dy/y = -dx
Lny =-x+lnc 1, y = c 1e (-x), y (0) = 1, C 1 = 1, then y = e (-x).