[m]y`=\frac{5}{2}\cdot (x-4)^{\frac{5}{2}-1}\cdot (x-4)`+5\cdot (-2)\cdot (2x^2+4x-1)^{-2-1}\cdot (2x^2+4x-1)`[/m]
[m]y`=\frac{5}{2}\cdot (x-4)^{\frac{3}{2}}- \frac{10}{(2x^2+4x-1)^3}\cdot (4x+4)[/m]
[m]y`=\frac{5}{2}\cdot \sqrt{(x-4)^3}- \frac{40(x+1)}{(2x^2+4x-1)^3}[/m]