A few days ago I asked about a problem with plotting a sum. You advise me to use Evaluate option, and that helped me very. But now I have a very similar problem, but i can't find the mistake. I have a equation: $$\sum_{i=0}^x {x\choose l}\cdot l^{10}\cdot(-1)^{(x-l)}$$ I want to draw this for $$x \in [0,10]$$ I used this command:
Plot[Evaluate[Sum[Binomial[x, l]*l^50*(-1)^(x - l), {l, 0, x}]], {x, 1,2}]
There are no errors, but also no graph. If I will expand the equation for $x=1$ I have: $${1\choose 0 }\cdot 0^{10}\cdot (-1)^{1-0} + {1 \choose 1}\cdot 1^{10}\cdot (-1)^{1-1} = 1$$
and for example for $x=5$ it is: $${5\choose 0 }\cdot 0^{10}\cdot (-1)^{5-0} + {5 \choose 1}\cdot 1^{10}\cdot (-1)^{5-1} + {5\choose 2 }\cdot 2^{10}\cdot (-1)^{5-2} + {5 \choose 3}\cdot 3^{10}\cdot (-1)^{5-3} + {5\choose 4 }\cdot 4^{10}\cdot (-1)^{5-4} + {5\choose 5 }\cdot 5^{10}\cdot (-1)^{5-5} = 5 103 000$$
So as you can see, there equation can be evaluated, so why I can't see any plotted points?
(-1)^(-0.5)
which is a complex number. You need to restrict x to integers, or take the Abs[ ] or plot over a range where you don't get complex-valued numbers. $\endgroup$