1) f(x)=√(4-8x)
ООФ: 4-8x≥0, 8x≤4, x≤1/2, x∈(-∞,1/2]
2)f(x)=6/(12x-3)
ООФ: 12x-3≠0, 12x≠3, x≠1/4, x∈(-∞,1/4)∨(1/4,∞)