a = b | ⋅ π a ⋅ π = b ⋅ π | ⋅ a a 2 π = a b π | + a 2 p i 2 a 2 π = a 2 π + a b π | − 2 a b π 2 a 2 π − 2 a b π = a 2 π − a b π | ( a − b ) ausklammern 2 a 2 π ( a − b ) = a 2 π ( a − b ) | : ( a − b ) 2 a 2 π = a 2 π | : a 2 2 π = π | − π π = 0 ◼ {\displaystyle {\begin{aligned}a&=b&&|\cdot \pi \\a\cdot \pi &=b\cdot \pi &&|\cdot a\\a^{2}\pi &=ab\pi &&|+a^{2}pi\\2a^{2}\pi &=a^{2}\pi \ +\ ab\pi &&|-2ab\pi \\2a^{2}\pi \ -\ 2ab\pi &=a^{2}\pi \ -\ ab\pi &&|\left(a-b\right){\text{ausklammern}}\\2a^{2}\pi \left(a-b\right)&=a^{2}\pi \left(a-b\right)&&|:\left(a-b\right)\\2a^{2}\pi &=a^{2}\pi &&|:a^{2}\\2\pi &=\pi &&|-\pi \\\pi &=0&&\blacksquare \end{aligned}}}
