More Chain Rule questions



All,

I have the function

(%i1) y(x):=(x^2-1)^10*(x^2+1)^15;

(%o1) y(x):=(x^2-1)^10*(x^2+1)^15

 

(%i2) diff(y(x),x);

(%o2) 20*x*(x^2-1)^9*(x^2+1)^15+30*x*(x^2-1)^10*(x^2+1)^14

 

manually this simplifies to

10*x*(5*x^2-1)*(x^2-1)^9*(x^2+1)^14 

 

however factor(%) yields

(%i3) factor(%);

(%o3) 10*(x-1)^9*x*(x+1)^9*(x^2+1)^14*(5*x^2-1)

 

What am I not seeing or doing incorrectly?

 

Thanks

Ron