Question

求学霸解答6，7，8

Answer 1

6.原式=[﹙a-b﹚²+(b-c)²+(c-a)²]÷2=3

追问

求学霸解答下面的，我会加分的

追答

7.2x+1=根号5 两边平方得x^2+x=1 即x^2=1-x 两边再平方得 x^4=x^2-2x+1 将x^4、x^2代入原式可得 2-2x 再将x的值代入得结果3-根号5

8.原式=(x+y+z)(x-y+z)(x+y-z)(y+z-x)

=(((x+z)^2-y^2)(y^2-(x-z)^2))
=y^2((x+z)^2+(x-z)^2)-y^4-(x+z)^2(x-z)^2
=y^2(2x^2+2z^2)-y^4-(x^2-z^2)^2
=2x^2y^2+2y^2z^2-y^4-x^4-z^4+2x^2z^2
=2x^2y^2+2y^2z^2+2x^2z^2-x^4-y^4-z^4

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