Well, a lot of these are built-in functions. For example
>> x = linspace(1,50,50);
>> plot(x,log(x))
>> plot(x,x)
>> plot(x,x.*log(x))
>> plot(x,x.^2)
I don't know what nj (j > 2) and cn (c > 1) are supposed to mean.
For the last one, you should look at the function factorial.
It's not clear from the context whether you're supposed to plot them on different graphs or all on the same graph. If all on the same graph, then you can use
>> hold on;
to freeze the current axes - that means that any new lines will get drawn on top of the old ones, instead of being drawn on a fresh set of axes.
In Matlab (and probably in Scilab) you can supply a "line spec" argument to the plot function, which tells it what color and style to draw the line in. For example,
>> figure
>> hold on
>> plot(x,log(x),'b')
>> plot(x,x/10,'r')
>> plot(x,x.^2/1000,'g')
Tells Matlab to plot the function f(x)=log(x) in blue, f(x)=x/10 in red and f(x)=x^2/1000 in green, which results in this plot:
