Vynásob dvojčleny:
\large \left( 7r - s\right) \cdot \left( 5t - 2u\right)
\large = 35rt- 14ru+ 5st - 2su
\large = 35rt+ 14ru- 5st - 2su
\large = 35rt- 14ru- 5st + 2su
\large = 35rt- 14ru- 5st - 2su