Find the fourth derivative of lnx^3-5x^2
if you mean
y = ln(x^3-5x^2) then using the properties of logs,
y = ln(x^2(x-5)) = ln(x^2) + ln(x-5) = 2lnx + ln(x-5)
y' = 2/x + 1/(x-5) = (3x-10)/(x^2-5x)
y" = -(3x^2-20x+50)/(x^2-5x)^2
y(3) = (6x^3-60x^2+300x-500)/(x^2-5x)^3
y(4) = -6(3x^4-40x^3+300x^2-1000x+1250)/(x^2-5x)^4