利用乘法公式计算(x+y)(x²+y²)-查字典问答网
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  利用乘法公式计算(x+y)(x²+y²)(x-y)(x的四次方+y四次方)(a-2b+3)(a+2b-3)[(x-y)²+(x+y)²](x²-y²)(m-n-3)²先化简,再求值[(a-1/2)²-(a+1/2)²](a+3),其中a=-2

  利用乘法公式计算

  (x+y)(x²+y²)(x-y)(x的四次方+y四次方)

  (a-2b+3)(a+2b-3)

  [(x-y)²+(x+y)²](x²-y²)

  (m-n-3)²

  先化简,再求值

  [(a-1/2)²-(a+1/2)²](a+3),其中a=-2

1回答
2020-06-15 07:01
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  (x+y)(x²+y²)(x-y)(x的四次方+y四次方)

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

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

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

  =x^8-y^8

  (a-2b+3)(a+2b-3)

  =[a-(2b-3)][a+(2b-3)]

  =a^2-(2b-3)^2

  =a^2-4b^2+12b-9

  [(x-y)²+(x+y)²](x²-y²)

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

  =2(x^4-y^4)

  =2x^4-2y^4

  (m-n-3)²

  =m^2+n^2+9-2mn-6m+6n

  [(a-1/2)²-(a+1/2)²](a+3)

  =[(a-1/2)+(a+1/2)][(a-1/2)-(a+1/2)](a+3)

  =2a(-1)(a+3)

  =-2a^2-6a

  将a=-2代入,得

  [(a-1/2)²-(a+1/2)²](a+3)

  =-2*(-2)^2-6*(-2)

  =4

2020-06-15 07:03:48

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