To show that the zero of the function is the square of the other, we factorize as follows:
8x^2-30x+27
factoring the above we get:
8x^2-12x-18x+27
factoring we obtain:
4x(2x-3)-9(2x-3)
=(2x-3)(4x-9)
from above roots we see that:
the zeros are:
x=3/2 and x=9/4
the second zero is the square of the first
