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bold left parenthesis bold italic a bold plus bold italic b bold right parenthesis to the power of bold 2 bold equals bold italic a to the power of bold 2 bold plus bold 2 bold italic a bold italic b bold plus bold italic b to the power of bold 2 bold left parenthesis bold italic a bold minus bold italic b bold right parenthesis to the power of bold 2 bold equals bold italic a to the power of bold 2 bold minus bold 2 bold italic a bold italic b bold plus bold italic b to the power of bold 2 bold left parenthesis bold italic a bold plus bold italic b bold right parenthesis bold times bold left parenthesis bold italic a bold minus bold italic b bold right parenthesis bold equals bold italic a to the power of bold 2 bold minus bold italic b to the power of bold 2   


Exemples:

left parenthesis x plus 3 right parenthesis squared equals x squared plus 2 times x times 3 plus 3 squared equals x squared plus 6 x plus 9 left parenthesis x minus 3 right parenthesis squared equals x squared minus 2 times x times 3 plus 3 squared equals x squared minus 6 x plus 9 left parenthesis x plus 3 right parenthesis times left parenthesis x minus 3 right parenthesis equals x squared minus 3 squared equals x squared minus 9

Observacions:

Si volem calcular, per exemple  left parenthesis 5 minus 3 right parenthesis squared podríem fer:

     · Aplicar la fórmula:    left parenthesis 5 minus 3 right parenthesis squared equals 5 squared minus 2 times 5 times 3 plus 3 squared equals 25 minus 30 plus 9 equals 34 minus 30 equals 4

     · Directament:  left parenthesis 5 minus 3 right parenthesis squared equals 2 squared equals 4

És obvi, que quan són nombres amb els que podem operar, és més senzill fer-ho directament.

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