Wzory:
y(x) = 1 / (1 + 25*x)
y'   = -(0.08 * x) / ((x^2 + 0.04)^2)

Warunek pocztkowy: y(-5) = 1 / 626


------ Euler (explicit) ------
y[-5]  = 1/626
y[n+1] = y[n] - h * (0.08 * x[n]) / ((x[n]^2 + 0.04)^2)
x[n+1] = x[n] + h


------ Euler (backward) ------
y[-5]  = 1/626
y[n+1] = y[n] - h * (0.08 * x[n+1]) / ((x[n+1]^2 + 0.04)^2)
x[n+1] = x[n] + h


------ Trapezoidal rule ------
y[-5]  = 1/626
y[n+1] = y[n] - h * 0.5 * ( ((0.08 * x[n]) / ((x[n]^2 + 0.04)^2)) + ((0.08 * x[n+1])/((x[n+1]^2 + 0.04)^2)) )
x[n+1] = x[n] + h