y=1/5x^5/2-1/3x^3/2
y'=1/5*5/2x^(5/2-1)-1/3*3/2x^(3/2-1)
=1/2x^3/2-1/2x^1/2
y=6/x+4/x^2+3/x^3
y'=-6/x^2+(-2x*4)/x^4+(-3x^2*3)/x^6
=-6/x^2-8/x^3-9/x^4