TeX Quellcode:

\begin{array}{rcl} \sum\limits_{i=1}^4 (2+i)x^i &=& (2+1)x^1+(2+2)x^2+(2+3)x^3+(2+4)x^4 \cr &=& 3x+4x^2+5x^3+6x^4 \cr &=& x(3+4x+5x^2+6x^3) \end{array}