Solve By Factorig:

x^(9/4)- 2x^(5/4)- 3x^(1/4)= 0

factor out x^(1/4):

x^(1/4)*(x^2 - 2x - 3) = 0
x^(1/4)*(x-3)*(x+1) = 0

So, when any of the factors is zero, the product is zero.

x = 0,3,-1