$w\left(-5\right)=\left(-5+1\right)\cdot \left(-5+2\right)\cdot \left(-5+3\right)\cdot \dots \cdot \left(-5+5\right)\cdot \dots \cdot \left(-5+10\right)=$  

$=\left(-5+1\right)\cdot \left(-5+2\right)\cdot \left(-5+3\right)\cdot \dots \cdot 0\cdot \dots \cdot \left(-5+10\right)=0$  

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$w\left(-8\right)=\left(-8+1\right)\cdot \left(-8+2\right)\cdot \left(-8+3\right)\cdot \dots \cdot \left(-8+8\right)\cdot \dots \cdot \left(-8+8\right)=$  

$=\left(-8+1\right)\cdot \left(-8+2\right)\cdot \left(-8+3\right)\cdot \dots \cdot 0\cdot \dots \cdot \left(-8+10\right)=0$  

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Mamy więc:

$-8\cdot w\left(-5\right)=-8\cdot 0=0$  

$-5\cdot w\left(-8\right)=-5\cdot 0=0$  

Stąd:

$-8\cdot w\left(-5\right)=-5\cdot w\left(-8\right)\text{c. n. d.}$