#1. 25
25 y`=(8x-5*x^(-4)+1*x^(-1)-x^(4/5))`= =8-5*(-4)x^(-5)+1*(-1)*x^(-2)-(4/5)x^((4/5)-1)= =8+(20/x^(5))-(1/x^(5))-(4/(5*x^(1/5)))