(1)已知m+n=4,则1/2m^2+mn+1/2n^2=(2)已知x+y=2,xy=-3,则xy^2+x^2y(3)已知a+b=5,ab=3,求代数式a^3b-2a^2b^2+ab^3(4)(2008^3-2*2008^2-2006)/(2008^3+2008^2-2009)(3)(4)要有过程!
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![(1)已知m+n=4,则1/2m^2+mn+1/2n^2=(2)已知x+y=2,xy=-3,则xy^2+x^2y(3)已知a+b=5,ab=3,求代数式a^3b-2a^2b^2+ab^3(4)(2008^3-2*2008^2-2006)/(2008^3+2008^2-2009)(3)(4)要有过程!](/uploads/image/z/2770557-69-7.jpg?t=%281%29%E5%B7%B2%E7%9F%A5m%2Bn%3D4%2C%E5%88%991%2F2m%5E2%2Bmn%2B1%2F2n%5E2%3D%282%29%E5%B7%B2%E7%9F%A5x%2By%3D2%2Cxy%3D-3%2C%E5%88%99xy%5E2%2Bx%5E2y%283%29%E5%B7%B2%E7%9F%A5a%2Bb%3D5%2Cab%3D3%2C%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8Fa%5E3b-2a%5E2b%5E2%2Bab%5E3%284%29%282008%5E3-2%2A2008%5E2-2006%29%2F%EF%BC%882008%5E3%2B2008%5E2-2009%EF%BC%89%283%29%284%29%E8%A6%81%E6%9C%89%E8%BF%87%E7%A8%8B%21)
(1)已知m+n=4,则1/2m^2+mn+1/2n^2=(2)已知x+y=2,xy=-3,则xy^2+x^2y(3)已知a+b=5,ab=3,求代数式a^3b-2a^2b^2+ab^3(4)(2008^3-2*2008^2-2006)/(2008^3+2008^2-2009)(3)(4)要有过程!
(1)已知m+n=4,则1/2m^2+mn+1/2n^2=
(2)已知x+y=2,xy=-3,则xy^2+x^2y
(3)已知a+b=5,ab=3,求代数式a^3b-2a^2b^2+ab^3
(4)(2008^3-2*2008^2-2006)/(2008^3+2008^2-2009)
(3)(4)要有过程!
(1)已知m+n=4,则1/2m^2+mn+1/2n^2=(2)已知x+y=2,xy=-3,则xy^2+x^2y(3)已知a+b=5,ab=3,求代数式a^3b-2a^2b^2+ab^3(4)(2008^3-2*2008^2-2006)/(2008^3+2008^2-2009)(3)(4)要有过程!
(1)已知m+n=4,则
1/2m^2+mn+1/2n^2=(m^2+2mn+n^2)/2=(m+n)^2/2=16/2=8
(2)已知x+y=2,xy=-3,则
xy^2+x^2y =xy(x+y)=-3*2=-6
(3)已知a+b=5,ab=3,代数式
a^3b-2a^2b^2+ab^3
=(a^3b+2a^2b^2+ab^3)-4a^2b^2
=ab(a^2+2ab+b^2)-4a^2b^2
=ab(a+b)^2-4a^2b^2
=3*5^2-4*3^2
=75-36=39
(4)(2008^3-2*2008^2-2006)/(2008^3+2008^2-2009)
=[2008^2(2008-2)-2006]/[2008^2(2008+1)-2009]
=(2008^2*2006-2006)/(2008^2*2009-2009)
=2006(2008^2-1)/[2009(2008^2-1)]
=2006/2009