计算题.(1)(x+2)(x-2)+x(3-x)(2) (x+1)^2+2(1-x)-x^2(3) (a-b+c)^2

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计算题.(1)(x+2)(x-2)+x(3-x)(2) (x+1)^2+2(1-x)-x^2(3) (a-b+c)^2
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计算题.(1)(x+2)(x-2)+x(3-x)(2) (x+1)^2+2(1-x)-x^2(3) (a-b+c)^2
计算题.
(1)(x+2)(x-2)+x(3-x)
(2) (x+1)^2+2(1-x)-x^2
(3) (a-b+c)^2

计算题.(1)(x+2)(x-2)+x(3-x)(2) (x+1)^2+2(1-x)-x^2(3) (a-b+c)^2
=x^2-4-x^2+3x=3x-4 =x^2+2x+1-2x-2-x^2=-1 =(a-b)^2+c^2+2c(a-b)=a^2+b^2-2ab+c^2+2bc-2ac

1.=3x-4
2.=3

(1)(x+2)(x-2)+x(3-x)
=x²-4+3-x²
=-1
(2) (x+1)^2+2(1-x)-x^2
=x²+2x+1+2-2x-x²
=3
(3) (a-b+c)^2
=(a-b)²+2c(a-b)+c²
=a²-2ab+b²+2ac-2bc+c²