y=[(3-4x)^(2/3)]/[(x^2+8)^(1/3)*(7+4x^3)^2]
x in (-oo:+oo)
x^2+(3/4)*x+1/8 = 0
x^2+3/4*x+1/8 = 0
DELTA = (3/4)^2-(1/8*1*4)
DELTA = 1/16
DELTA > 0
x = ((1/16)^(1/2)-3/4)/(1*2) or x = (-(1/16)^(1/2)-3/4)/(1*2)
x = -1/4 or x = -1/2
x in { -1/2, -1/4 }