运用公式计算1.〔(3a+b)(3a-b)〕²2.-查字典问答网
分类选择

来自崔航的问题

  运用公式计算1.〔(3a+b)(3a-b)〕²2.(2x+y)²(2x-y)²3.(5m+2n)²—(5m-2n)²4.(-5x+3y-2z)²5.(-a-b+3)²6.(-3x-5y)²7.(-2a+3b-5c)(-2a-3b+5c)8.(3m-4n+2)(-3m-4n-2)9

  运用公式计算

  1.〔(3a+b)(3a-b)〕²

  2.(2x+y)²(2x-y)²

  3.(5m+2n)²—(5m-2n)²

  4.(-5x+3y-2z)²

  5.(-a-b+3)²

  6.(-3x-5y)²

  7.(-2a+3b-5c)(-2a-3b+5c)

  8.(3m-4n+2)(-3m-4n-2)

  9.已知x+x分之一=5求x²+x²分之一的值

  10.已知a-b=7ab=2求a²+b²的值

  11.已知x²-8x+y²+6y+25=0求x及y的值

1回答
2020-04-24 14:40
我要回答
请先登录
程义民

  1.[(3a+b)(3a-b)]^2

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

  =(9a^2-b^2)^2

  =81a^4-18a^2b^2+b^4

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

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

  =[(2x)^2-y^2]^2

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

  =16x^4-8x^2y^2+y^4

  3.(5m+2n)^2—(5m-2n)^2

  =[(5m+2n)+(5m-2n)][(5m+2n)-(5m-2n)]

  =(10m)(4n)

  =40mn

  4.(-5x+3y-2z)^2

  =25x^2-15xy+10xz-15xy+9y^2-6yz+10xz-6yz+4z^2

  =25x^2-30xy+20xz+9y^2-12yz+4z^2

  5.(-a-b+3)^2

  =a^2+ab-3a+ab+b^2-3b-3a-3b+9

  =a^2+2ab-6a+b^2-6b+9

  6.(-3x-5y)²

  =9x^2+30xy+25y^2

  7.(-2a+3b-5c)(-2a-3b+5c)

  =[-2a+(3b-5c)][-2a-(3b-5c)]

  =(-2a)^2-(3b-5c)^2

  =4a^2-9b^2+30bc-25c^2

  8.(3m-4n+2)(-3m-4n-2)

  =-(3m-4n+2)(3m+4n+2)

  =-[(3m+2)-4n][(3m+2)+4n]

  =-[(3m+2)^2-(4n)^2]

  =-9m^2-12m-4+16n^2

  9.[x+(1/x)]^2=x^2+2+(1/x)^2=25

  x^2+1/x^2=25-2=23

  10.a^2+b^2=(a-b)^2-2ab=7^2-2×2=49-4=45

  11.x^2-8x+y^2+6y+25=0

  (x^2-8x+16)+(y^2+6y+9)=0

  (x-4)^2+(y+3)^2=0

  ∵(x-4)^2和(y+3)^2恒≥0

  ∴x-4=0,y+3=0

  x=4,y=-3

2020-04-24 14:42:23

最新问答

推荐文章

猜你喜欢

附近的人在看

推荐阅读

拓展阅读

  • 大家都在看
  • 小编推荐
  • 猜你喜欢
  •