1 ---- x(x-1)-(x^2-y)=-2,求(x^2+y^2)/2-xy的值2 ---- 试说明不论x,y取什么有理数,多项式x^2+y^2-2x+2y+3的值总是正数.^2大家都知道的吧,就是平方,waiting.
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![1 ---- x(x-1)-(x^2-y)=-2,求(x^2+y^2)/2-xy的值2 ---- 试说明不论x,y取什么有理数,多项式x^2+y^2-2x+2y+3的值总是正数.^2大家都知道的吧,就是平方,waiting.](/uploads/image/z/3174931-19-1.jpg?t=1+----+x%28x-1%29-%28x%5E2-y%29%3D-2%2C%E6%B1%82%28x%5E2%2By%5E2%29%2F2-xy%E7%9A%84%E5%80%BC2+----+%E8%AF%95%E8%AF%B4%E6%98%8E%E4%B8%8D%E8%AE%BAx%2Cy%E5%8F%96%E4%BB%80%E4%B9%88%E6%9C%89%E7%90%86%E6%95%B0%2C%E5%A4%9A%E9%A1%B9%E5%BC%8Fx%5E2%2By%5E2-2x%2B2y%2B3%E7%9A%84%E5%80%BC%E6%80%BB%E6%98%AF%E6%AD%A3%E6%95%B0.%5E2%E5%A4%A7%E5%AE%B6%E9%83%BD%E7%9F%A5%E9%81%93%E7%9A%84%E5%90%A7%2C%E5%B0%B1%E6%98%AF%E5%B9%B3%E6%96%B9%2Cwaiting.)
1 ---- x(x-1)-(x^2-y)=-2,求(x^2+y^2)/2-xy的值2 ---- 试说明不论x,y取什么有理数,多项式x^2+y^2-2x+2y+3的值总是正数.^2大家都知道的吧,就是平方,waiting.
1 ---- x(x-1)-(x^2-y)=-2,求(x^2+y^2)/2-xy的值
2 ---- 试说明不论x,y取什么有理数,多项式x^2+y^2-2x+2y+3的值总是正数.
^2大家都知道的吧,就是平方,
waiting.
1 ---- x(x-1)-(x^2-y)=-2,求(x^2+y^2)/2-xy的值2 ---- 试说明不论x,y取什么有理数,多项式x^2+y^2-2x+2y+3的值总是正数.^2大家都知道的吧,就是平方,waiting.
1.
∵x(x-1)-(x^2-y)=-2
∴x^2-x-x^2+y=-2
x-y=2
∵(x-y)^2=x^2+y^2-2xy=4
∴x^2+y^2=4+2xy
∴(x^2+y^2)/2-xy=(4+2xy)/2-xy=2+xy-xy=2
2.x^2+y^2-2x+2y+3=x^2-2x+1+y^2+2y++1+1
=(x-1)^2+(y+1)^2+1
∵(x-1)^2、(y+1)^2均大于等于0
∴x^2+y^2-2x+2y+3=(x-1)^2+(y+1)^2+1>0
请选我吧````(^-^)
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