u_1 = 5 (slider from 0 to 20, step 0.1)
q = 0.9 (slider from -2 to 2, step 0.1)
u_{n+1}(x) = u_1 * q^(x)
n = 13 (slider from 0 to 20, step 1)
u_n: (n, u_{n+1}(n))
texte1: "\frac{u_{n+1}}{u_n} = " + q