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care este formula (x-y) la 3​

Răspuns :

(x-y)³ = (x-y)(x-y)² = (x-y)(x²-2xy+y²) =

= x³-2x²y+xy²-x²y+2xy²-y³ =

= x³-y³-3x²y+3xy² =

= x³-y³-3xy(x-y)

=> (x-y)³ = x³-y³-3xy(x-y)