I am trying to get something in the form of a $\Sigma (\dots) * \alpha_i = (\dots)$ from the output of the code below. The thing is that I cannot figure out how to tell Mathematica to "collapse" down to a single sum and factor out the $\alpha_i$.
Thank you,
John
$Assumptions =
i \[Element] Integers && j \[Element] Integers &&
n \[Element] Integers && i \[Element] Constant &&
j \[Element] Constant && n \[Element] Constant;
r[t_] = (D[#, {t, 2}] - t*D[#, t] + 1/6*# - (-3)) &;
inner[x_] = (Integrate[
Simplify[
ComplexExpand[#1 Conjugate[#2],
TargetFunctions -> {Re, Im}]], {x, 0, 10}]) &;
uB = 5 - \[Pi]/5*x;
\[Phi][i_] = x^i*(10 - x);
uApp = uB + Sum[Subscript[\[Alpha], i]*\[Phi][i], {i, 1, n}];
(r[x][uApp] /. x -> (10 - 0)/(n + 1)*j) == 0
j \[Element] Constant && n \[Element] Constant, becauseConstantisn't a domain of which something can be an element. To distinguish constants in a differentiation you don't have to do anything special. It's the opposite case that requires a little work - see here. – Jens Jan 22 at 4:11