# My plot is not showing any curves

I want to see what will happen for different values of the parameters $k_1$ and $k_2$, but all I see is an empty plot.

Can someone help me?

Manipulate[
Plot[
{
x -> Function[{t}, 1 - (-1 + k2*E^(k1*t + k1 )) /(-1 + k1*E^(k1*t + k1 ) + k2*E^(k1*t + k1 ))]
, u -> Function[{t}, (-1 + k2*E^(k1*t + k1) ) /(-1 + E^(k1* t + k1 ) *k1 + E^(k1 t C[1] + k1 C[1] C[2]) *k2)]
}
, {t, 0, 100}
]
, {k1, 0, 10}
, {k2, 0, 10}
]


A rule ( -> ) does not work like a function definition here. If you instead define x and u as functions of t, k1 and k2 the plot works as you would like. It is also useful to set the PlotRange so it does not automatically rescale with the function.

x[t_, k1_, k2_] :=
1 - (-1 + k2*E^(k1*t + k1))/(-1 + k1*E^(k1*t + k1) +
k2*E^(k1*t + k1));
u[t_, k1_, k2_] := (-1 + k2*E^(k1*t + k1))/(-1 + E^(k1*t + k1)*k1 +
E^(k1 t C[1] + k1 C[1] C[2])*k2)

Manipulate[
Plot[
{x[t, k1, k2], u[t, k1, k2]},
{t, 0, 100},
PlotRange -> {-2, 2}
],
{k1, 0, 10},
{k2, 0, 10}
]