1. $$a1 = \frac{1}{x}$$
2. $$a2 = \frac{a1}{x} = \frac{1}{x^2}$$
3. $$a3 = \frac{a2}{x} = \frac{1}{x^3}$$
4. $$a4 = \frac{a3}{x} = \frac{1}{x^4}$$
5. $$y = a1 + a2 = \frac{1}{x} + \frac{1}{x^2}$$
6. $$y = y + a3 = \frac{1}{x} + \frac{1}{x^2} + \frac{1}{x^3}$$
7. $$y = y + a4 = \frac{1}{x} + \frac{1}{x^2} + \frac{1}{x^3} + \frac{1}{x^4}$$
Итоговая формула: $$y = \frac{1}{x} + \frac{1}{x^2} + \frac{1}{x^3} + \frac{1}{x^4}$$