Đáp án:
1. `1/3`
2. `x=1;x=2`
Giải thích các bước giải:
Bài `1:`
`x^2-2y^2=xy`
`to x^2-2y^2-xy=0`
`to x^2-y^2-y^2-xy=0`
`to (x+y)(x-y)-y(y+x)=0`
`to (x+y)(x-y-y)=0`
`to (x+y)(x-2y)=0`
`to x-2y=0` ( vì `x+y ne 0` )
`to x=2y`
`P=(x-y)/(x+y)=(2y-y)/(2y+y)=y/(3y)=1/3`
Bài `2:`
`x^3-5x^2+8x-4=0`
`to x^3-4x^2-x^2+4x+4x-4=0`
`to (x^3-x^2)-(4x^2-4x)+(4x-4)=0`
`to x^2.(x-1)-4x.(x-1)+4.(x-1)=0`
`to (x-1).(x^2-4x+4)=0`
`to (x-1).(x^2-2x-2x+4)=0`
`to (x-1).[x.(x-2)-2.(x-2)]=0`
`to (x-1).(x-2).(x-2)=0`
`to` \(\left[ \begin{array}{l}x-1=0\\x-2=0\end{array} \right.\) `to` \(\left[ \begin{array}{l}x=1\\x=2\end{array} \right.\)
