1.x+y=6,则1/6x^2+1/3xy+1/6y^2=____2.(x-1) [ x^n+x^(n-1)+x^(n-2)+……+x+1 ]=_____ (n为正整数).3.x^2-3x-1=0,求x^2+1/x^2的值 4.已知x^2-16x+y^2-6y+73=0,求xy值5.已知a-b=b-c=6,且a^2+b^2+c^2=162,求ab+bc+ac的值6.若a.b.c是△ABC的
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/27 03:53:02
![1.x+y=6,则1/6x^2+1/3xy+1/6y^2=____2.(x-1) [ x^n+x^(n-1)+x^(n-2)+……+x+1 ]=_____ (n为正整数).3.x^2-3x-1=0,求x^2+1/x^2的值 4.已知x^2-16x+y^2-6y+73=0,求xy值5.已知a-b=b-c=6,且a^2+b^2+c^2=162,求ab+bc+ac的值6.若a.b.c是△ABC的](/uploads/image/z/12704860-28-0.jpg?t=1.x%2By%3D6%2C%E5%88%991%2F6x%5E2%2B1%2F3xy%2B1%2F6y%5E2%3D____2.%EF%BC%88x-1%29+%5B+x%5En%2Bx%5E%28n-1%29%2Bx%5E%28n-2%29%2B%E2%80%A6%E2%80%A6%2Bx%2B1+%5D%3D_____+%EF%BC%88n%E4%B8%BA%E6%AD%A3%E6%95%B4%E6%95%B0%EF%BC%89.3.x%5E2-3x-1%3D0%2C%E6%B1%82x%5E2%2B1%2Fx%5E2%E7%9A%84%E5%80%BC+4.%E5%B7%B2%E7%9F%A5x%5E2-16x%2By%5E2-6y%2B73%3D0%2C%E6%B1%82xy%E5%80%BC5.%E5%B7%B2%E7%9F%A5a-b%3Db-c%3D6%2C%E4%B8%94a%5E2%2Bb%5E2%2Bc%5E2%3D162%2C%E6%B1%82ab%2Bbc%2Bac%E7%9A%84%E5%80%BC6.%E8%8B%A5a.b.c%E6%98%AF%E2%96%B3ABC%E7%9A%84)
1.x+y=6,则1/6x^2+1/3xy+1/6y^2=____2.(x-1) [ x^n+x^(n-1)+x^(n-2)+……+x+1 ]=_____ (n为正整数).3.x^2-3x-1=0,求x^2+1/x^2的值 4.已知x^2-16x+y^2-6y+73=0,求xy值5.已知a-b=b-c=6,且a^2+b^2+c^2=162,求ab+bc+ac的值6.若a.b.c是△ABC的
1.x+y=6,则1/6x^2+1/3xy+1/6y^2=____
2.(x-1) [ x^n+x^(n-1)+x^(n-2)+……+x+1 ]=_____ (n为正整数).
3.x^2-3x-1=0,求x^2+1/x^2的值
4.已知x^2-16x+y^2-6y+73=0,求xy值
5.已知a-b=b-c=6,且a^2+b^2+c^2=162,求ab+bc+ac的值
6.若a.b.c是△ABC的三边,且a^2+b^2+c^2+89=6a+8b+16c,求△ABC周长
1.x+y=6,则1/6x^2+1/3xy+1/6y^2=____2.(x-1) [ x^n+x^(n-1)+x^(n-2)+……+x+1 ]=_____ (n为正整数).3.x^2-3x-1=0,求x^2+1/x^2的值 4.已知x^2-16x+y^2-6y+73=0,求xy值5.已知a-b=b-c=6,且a^2+b^2+c^2=162,求ab+bc+ac的值6.若a.b.c是△ABC的
1、6 注:1/6*(x+y)^2
2、x^(n+1)-1 注:展开,除第一项x^(n+1)和最有一项-1外,都消掉了
3、11 注:x-3-1/x=0,x-1/x=3,两边平方,x^2-2+1/x^2=9
4、24 注:(x-8)^2 + (y-3)^2 = 0,x=8 y=3
5、54 注:a-c=a-b + b-c =12,a^2+b^2+c^2=1/2*[(a-b)^2+(b-c)^2+(a-c)^2] + (ab+bc+ac)=162
6、15 注:(a-3)^2 + (b-4)^2 + (c-8)^2 = 0,a=3 b=4 c=8,a+b
1.33
(1)36
对于填空题,可以用特殊值法
(1)令x=y=3,带入得
(2)x^(n+1)-1 等比数列求和公式变形
(3)将x^2=3x+1 带入所求式,再计算
(4)分别对x、y配方,求得x=8,y=3 这种题一般都是先配方再求值