Intricate proof by induction: $2+8+24+64+...+(n)(2^n)=2(1+(n-1)(2^n))$ Help the King out...
$$2+8+24+64+...+(n)(2^n)=2(1+(n-1)(2^n))$$
I am at the step where I am proving $P(k+1)$ to be true:
$$2(1+(k-1)(2^k))+(k+1)((2)^{k+1}))=2(1+((k+1)-1)(2^{k+1}))$$

See part I of my answer here for the background to the following systematic approach.

We have here $f(k) = k\cdot2^k$ and $g(n) = 2 + (n-1)\cdot 2^{n+1}$
Inductive step: 
1: Assume true for $n$, that is $\sum_{k=1}^{n}f(k) = g(n)\tag{1}$
2: Let $m = n + 1$
$\begin{align}f(m) &= m\cdot2^m\\\\ g(m) - g(m-1) &= \left(2 + (m-1)\cdot2^{m+1}\right) - \left(2 + (m-2)\cdot2^{m}\right)\\&=(2m-2 - m + 2)\cdot2^m\\&=m\cdot2^m\\\\\therefore f(m) &= g(m) - g(m-1)\\\text{i.e }  \color{blue}{f(n+1)}&=\color{blue}{g(n+1) - g(n)}\tag{2}\end{align}$
We thus have
$$\begin{align}\sum_{k=1}^{n+1}f(k)=\sum_{k=1}^{n}f(k) + f(n+1) = \underbrace{g(n)}_{\text{from }(1)} + \underbrace{g(n+1) - g(n)}_{\text{from }(2)} = g(n+1)\end{align}$$
implies that the statement is true for $n+1$.
