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thanhviet2018
2 năm trước
1, Chứng minh các hằng đẳng thức: a, $(a + b + c)^{3}$ - $a^{3}$ - $b^{3}$ - $c^{3}$ = 3 (a + b) (b + c) (c + a) b, $a^{3}$ + $b^{3}$ + $c^{3} - 3abc = (a + b + c) ($a^{2}$ + $b^{2}$ + $c^{2} - ab - bc - ac) 2, a, Cho x + y = 1. Tính GTBT $x^{3}$ + $y^{3}$ + 3xy b, Cho x - y = 1. Tính GTBT $x^{3}$ - $y^{3}$ - 3xy Mong mn giúp!
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