(1)正数x,y满足x^2-y^2=2xy,求(x-y)/(x+y) (2)已知x+y=1,求x^3+y^3+3xy的值 (最好有具体过程,好的我会追加,答出一个或两个都可以)难道我不去做吗?一楼的你谁啊,你都懂啊
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/24 18:34:21
![(1)正数x,y满足x^2-y^2=2xy,求(x-y)/(x+y) (2)已知x+y=1,求x^3+y^3+3xy的值 (最好有具体过程,好的我会追加,答出一个或两个都可以)难道我不去做吗?一楼的你谁啊,你都懂啊](/uploads/image/z/2553196-4-6.jpg?t=%EF%BC%881%EF%BC%89%E6%AD%A3%E6%95%B0x%2Cy%E6%BB%A1%E8%B6%B3x%5E2-y%5E2%3D2xy%2C%E6%B1%82%28x-y%29%2F%28x%2By%29+%282%29%E5%B7%B2%E7%9F%A5x%2By%3D1%2C%E6%B1%82x%5E3%2By%5E3%2B3xy%E7%9A%84%E5%80%BC+%28%E6%9C%80%E5%A5%BD%E6%9C%89%E5%85%B7%E4%BD%93%E8%BF%87%E7%A8%8B%2C%E5%A5%BD%E7%9A%84%E6%88%91%E4%BC%9A%E8%BF%BD%E5%8A%A0%2C%E7%AD%94%E5%87%BA%E4%B8%80%E4%B8%AA%E6%88%96%E4%B8%A4%E4%B8%AA%E9%83%BD%E5%8F%AF%E4%BB%A5%29%E9%9A%BE%E9%81%93%E6%88%91%E4%B8%8D%E5%8E%BB%E5%81%9A%E5%90%97%EF%BC%9F%E4%B8%80%E6%A5%BC%E7%9A%84%E4%BD%A0%E8%B0%81%E5%95%8A%EF%BC%8C%E4%BD%A0%E9%83%BD%E6%87%82%E5%95%8A)
(1)正数x,y满足x^2-y^2=2xy,求(x-y)/(x+y) (2)已知x+y=1,求x^3+y^3+3xy的值 (最好有具体过程,好的我会追加,答出一个或两个都可以)难道我不去做吗?一楼的你谁啊,你都懂啊
(1)正数x,y满足x^2-y^2=2xy,求(x-y)/(x+y)
(2)已知x+y=1,求x^3+y^3+3xy的值
(最好有具体过程,好的我会追加,答出一个或两个都可以)
难道我不去做吗?一楼的你谁啊,你都懂啊
(1)正数x,y满足x^2-y^2=2xy,求(x-y)/(x+y) (2)已知x+y=1,求x^3+y^3+3xy的值 (最好有具体过程,好的我会追加,答出一个或两个都可以)难道我不去做吗?一楼的你谁啊,你都懂啊
(1)正数x,y满足x^2-y^2=2xy,求(x-y)/(x+y)
(x-y)/(x+y)
=(x-y)(x+y)/[(x+y)^2]
=(x^2-y^2)/[x^2+y^2+2xy]
=2xy/[x^2+y^2+x^2-y^2]
=2xy/(2x^2)
=y/x
x^2-y^2=2xy
x^2-2xy-y^2=0
解出 x=(1+√2)y 或者 x=(1-√2)y
所以原式=y/x=√2-1 或者 -√2-1
(2)已知x+y=1,求x^3+y^3+3xy的值
x^3+y^3+3xy
=(x+y)(x^2-xy+y^2)+3xy
=1*(x^2-xy+y^2)+3xy
=x^2-xy+y^2+3xy
=(x+y)^2
=1
作业要自己做,别人不可能帮你考大学
(x-y)/(x+y)
=(x-y)(x+y)/[(x+y)^2]
=(x^2-y^2)/[x^2+y^2+2xy]
=2xy/[x^2+y^2+x^2-y^2]
=2xy/(2x^2)
=y/x
x^2-y^2=2xy
x^2-2xy-y^2=0
解出 x=(1+√2)y 或者 x=(1-√2)y
所以原式=y/x=√2-1 或者 -√2-1