y=1+36x·(x+3)^(-2)
y'=36·(x+3)^(-2)+36x·[(x+3)^(-2)]'
=36·(x+3)^(-2)+36x·(-2)·(x+3)^(-3)
=36(3-x)·(x+3)^(-3)
y''=-36·(x+3)^(-3)+36x·[(x+3)^(-3)]
=-36·(x+3)^(-3)+36(3-x)·(-3)·(x+3)^(-4)
=36(x+3)^(-4)·[-(x+3)-3(3-x)]
=36(x+3)^(-4)·(2x-6)
=72(x+3)^(-4)·(x-3)