Why does the collect command work for some expressions and not for others. Here is a screen shot

I assume the collect command is supposed to rewrite the expression in terms of the variable descending order.

p := expand((a^2+2*x)*(a^2+2*x));
                        4      2        2   2
                       a  + 4 a  x + 4 x

collect(p, x);
                        4      2        2   2
                       a  + 4 a  x + 4 x

Does not work.

But if you look at the screenshot , it works for other expressions.

Hi I am reading this help document

http://www.maplesoft.com/support/help/Maple/view.aspx?path=SpaceCurve

and I cannot get maple to plot the same exact graph on that page, I receive this error

http://prntscr.com/8gzpt4

It only lets me plot 3 dimensional curves http://prntscr.com/8gzsry

When I downloaded the help document, the command executed. I cannot get it to work on my worksheet.

I even tried adding with(Student[VectorCalculus] ): and that did not help. 

I am clueless why this is not working.

Is there a way to upload a maple worksheet so you can see the error.

I'm not sure why im getting a complex solution for evalf(h(-1/2)). Posted screenshot here:

http://prntscr.com/8abmta

The answer should be positive 6*2^(2/3) ≈ 9.52

 The computer returns

h(-1/2) =

=

The problem is that evalf((-1)^(1/3)) you get 0.500 + .866I

Is there no way to evaluate a second derivative of a real valued function which has a fractional exponent without receiving complex results? I don't have the time to look at each function and try to figure out what went wrong. I want to plug in any x value into a function defined for all reals and get a real result.

I tried  assume(x , 'real' ) , that did not do anything.

WHen I type:

I get nothing, a blank box. But if I change the code slightly, by squaring both sides, then it works.

What is the reason for this. I uploaded an image of the output:  http://prntscr.com/752mtd