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a)Demonstrati ca = (a+b)²=a²+2ab+b²
b)Demonstrati ca = (a-b)²=a²-2ab+b²
c) Demonstrati ca = (a+b)x(a-b) = a²-b²

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Răspuns :

A)(a+b)²=(a+b)(a+b)=a²+ab+ba+b²=a²+2ab+b²
B)(a-b)²=(a-b)(a-b)=a²-ab-ba+b²=a²-2ab+b²
C)(a+b)×(a-b)=a²+ab-ba-b²=a²-b²

(a+b)²=(a+b)(a+b)=a²+ab+ab+b²=a²+2ab+b²
(a-b)²=(a-b)(a-b)=a²-ab-ab+b²⇒a²-2ab+b²
(a+b)(a-b)=a²-ab+ab-b²=a²-b²
sucees