y = ((x+1)/(x^2+3))^2
y` = 2*((x+1)/(x^2+3)) * ((x+1)/(x^2+3))` =
= 2*((x+1)/(x^2+3)) * ((x+1)`*(x^2+3)-(x+1)*(x^2+3)`) /(x^2+3)^2 =
= 2*((x+1)/(x^2+3)) * ((x^2+3)-(x+1)*(2x)) /(x^2+3)^2 =
= 2*((x+1)/(x^2+3)) * (x^2+3-2x^2-2x) /(x^2+3)^2 =
= 2*((x+1)/(x^2+3)) * (-x^2+3-2x) /(x^2+3)^2 =
=- 2*(x+1)*(x^2+2x-3) /(x^2+3)^3 - в таком виде можно оставить