Đáp án:1) (x+1/3)^3=x^3+3.x^2.1/3+3.x.(1/3)^2+(1/3)^3
=x^3+x^2+1/3 x +1/27
2) (3x-2y)^2=(3x)^2-2.3x.2y+(2y)^2
=9 x^2-12x+4 y^2
3)(2x-1/2)^2=4x^2-2x+1/4
4) (1/3x-1/2y)^2=1/9x^2-1/3xy+1/4y^2
5)(3x+1)(3x-1)=(3x)^2-1^2
=9x^2-1
6)(x/2-y) (x/2+y)=x^2/4-y^2
7)(x/2-2y)^2=x^2/4- 2xy+4y^2
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