代数式及恒等变形1.已知/a-8b/+(4b-1)^2+根号(8c-3a)=0,求a+b+c的值.2.已知x^2+y^2+z^2-2x+4y-6z+14=0,求x+y+z的值.3.已知x^2+xy+y=14,y^2+xy+x=28,求x+y的值.4.已知a+b+c=1,a^2+b^2+c^2=2,求ab+bc+ca=的值.5.已知a,b为有理数,
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![代数式及恒等变形1.已知/a-8b/+(4b-1)^2+根号(8c-3a)=0,求a+b+c的值.2.已知x^2+y^2+z^2-2x+4y-6z+14=0,求x+y+z的值.3.已知x^2+xy+y=14,y^2+xy+x=28,求x+y的值.4.已知a+b+c=1,a^2+b^2+c^2=2,求ab+bc+ca=的值.5.已知a,b为有理数,](/uploads/image/z/6677308-28-8.jpg?t=%E4%BB%A3%E6%95%B0%E5%BC%8F%E5%8F%8A%E6%81%92%E7%AD%89%E5%8F%98%E5%BD%A21.%E5%B7%B2%E7%9F%A5%2Fa-8b%2F%2B%284b-1%29%5E2%2B%E6%A0%B9%E5%8F%B7%EF%BC%888c-3a%EF%BC%89%3D0%2C%E6%B1%82a%2Bb%2Bc%E7%9A%84%E5%80%BC.2.%E5%B7%B2%E7%9F%A5x%5E2%2By%5E2%2Bz%5E2-2x%2B4y-6z%2B14%3D0%2C%E6%B1%82x%2By%2Bz%E7%9A%84%E5%80%BC.3.%E5%B7%B2%E7%9F%A5x%5E2%2Bxy%2By%3D14%2Cy%5E2%2Bxy%2Bx%3D28%2C%E6%B1%82x%2By%E7%9A%84%E5%80%BC.4.%E5%B7%B2%E7%9F%A5a%2Bb%2Bc%3D1%2Ca%5E2%2Bb%5E2%2Bc%5E2%3D2%2C%E6%B1%82ab%2Bbc%2Bca%3D%E7%9A%84%E5%80%BC.5.%E5%B7%B2%E7%9F%A5a%2Cb%E4%B8%BA%E6%9C%89%E7%90%86%E6%95%B0%2C)
代数式及恒等变形1.已知/a-8b/+(4b-1)^2+根号(8c-3a)=0,求a+b+c的值.2.已知x^2+y^2+z^2-2x+4y-6z+14=0,求x+y+z的值.3.已知x^2+xy+y=14,y^2+xy+x=28,求x+y的值.4.已知a+b+c=1,a^2+b^2+c^2=2,求ab+bc+ca=的值.5.已知a,b为有理数,
代数式及恒等变形
1.已知/a-8b/+(4b-1)^2+根号(8c-3a)=0,求a+b+c的值.
2.已知x^2+y^2+z^2-2x+4y-6z+14=0,求x+y+z的值.
3.已知x^2+xy+y=14,y^2+xy+x=28,求x+y的值.
4.已知a+b+c=1,a^2+b^2+c^2=2,求ab+bc+ca=的值.
5.已知a,b为有理数,且2a^2-2ab+b^2+4a+4=0,求a^2b+ab^2的值.
代数式及恒等变形1.已知/a-8b/+(4b-1)^2+根号(8c-3a)=0,求a+b+c的值.2.已知x^2+y^2+z^2-2x+4y-6z+14=0,求x+y+z的值.3.已知x^2+xy+y=14,y^2+xy+x=28,求x+y的值.4.已知a+b+c=1,a^2+b^2+c^2=2,求ab+bc+ca=的值.5.已知a,b为有理数,
1.已知/a-8b/+(4b-1)^2+根号(8c-3a)=0,求a+b+c的值.
a-8b=0 4b-1=0 8c-3a=0,所以a+b+c=3
2.已知x^2+y^2+z^2-2x+4y-6z+14=0,求x+y+z的值.
用完全平方来配方得到(x-1)^2+(y+2)^2+(z-3)^2=0
所以x=1 y=-2 z=3,所以x+y+z=2
3.已知x^2+xy+y=14,y^2+xy+x=28,求x+y的值.
把x^2+xy+y=14,y^2+xy+x=28两式相加,得(x+y)^2+(x+y)=42
(x+y)(x+y+1)=42
相邻两数相乘能得42的只有6、7或-6、-7
所以x+y=13或-13
4.已知a+b+c=1,a^2+b^2+c^2=2,求ab+bc+ca=的值.
由完全平方变形,最后可以算得ab+bc+ca=3/2
5.已知a,b为有理数,且2a^2-2ab+b^2+4a+4=0,求a^2b+ab^2的值.
同样由完全平方变形得到(a-b)^2+(a+2)^2=0
所以a=-2,b=-2
所以a^2b+ab^2=-16