a)
[tex]x\not =0\\\\\\\dfrac{2}{x}>1\\\\2x>x^2\\x^2-2x<0\\x(x-2)<0\\x\in(0,2)[/tex]
b)
[tex]x\not=0\\\\\\\dfrac{1}{x}\leq4\\\\x\leq4x^2\\4x^2-x\geq0\\x(4x-1)\geq0\\x\in(-\infty,0\rangle\cup\left\langle\dfrac{1}{4},\infty\right)\\\\\\x\in(-\infty,0\rangle\cup\left\langle\dfrac{1}{4},\infty\right)\wedge x\not=0\\x\in(-\infty,0)\cup\left\langle\dfrac{1}{4},\infty\right)[/tex]
