y = 5lnx Determine whether the function is a solution of the differential equation y^((4)) - 16y = 0

Given
y = 5ln(x)
y' = 5/x
y''=-5/x^2
y'''=10/x^3
y''''=-30/x^4
so we have to check whether y^((4)) -16y=0
y'''' -16y=-30/x^4 -16(5ln(x)) != 0   
So it's not a solution to the differential equation.