2 câu trả lời
=2.(a3+b3)+3.(a2+b2)
=2.(a+b).(a2−ab+b2)+4.[(a+b)2−2ab]
=2.(−1).(a2−ab+b2)+4.(1−2ab)
−(−2).(a2−ab+b2)+4−8ab
=−2a2+2ab−2b2−8ab+4
=−2a2−2b2−6ab+4
=−2.[(a+b)2−2ab]−6ab+4
=−2.(1−2ab)−6ab+4
=−2+4ab−6ab+4
=2−2ab
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