计算下列公式（1）(x-1/x)2（2）（a+2b)2+(a-2b)2(3)(2x-3y)2-(2x+3y)(2x-3y
1个回答
1）(x-1/x)^2=x^2-2+1/x^2
2）（a+2b)^2+(a-2b)^2=a^2+4ab+4b^2+a^2-4ab+4b^2=2a^2+8b^2
3)(2x-3y)2-(2x+3y)(2x-3y)=4x^2-12xy+9y^2-4x^2+9y^2=18y^2-12xy
4)2(x+2)2-(x-2)(x+2)=(x+3)(x-1)-3
2x^2+8x+8-x^2+4=x^2+2x-3-3
6x=-18
X=-3
(5)(0.5x+y/3)^2
=x^2
/4+xy/3+y^2
/9
(6)(3/2a-2/3b)2
=9a^2
/4-2ab+4b^2
/9
(7)(2m+3n)^2-(2m-3n)^2
=4m^2+12
mn+9n^2
-4m^2+12
mn-9n^2
=24mn
(8)(x-3)(x+3)-(x-3)^2
=x^2
-9-x^2+6x-9
=6x-18
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