`Delta'=(-1)^2-(2m-5)=1-2m+5=6-2m`

Pt có `2` no pb `<=>Delta'>0<=>6-2m>0<=>m<3`

Viet:`{(x_1+x_2=2),(x_1x_2=2m-5):}`

Đề:`(x_1^2-2)(x_2^2-2)=9`

`<=>x_1^2x_2^2-2x_1^2-2x_2^2+4-9=0`

`<=>(x_1x_2)^2-2(x_1^2+x_2^2)-5=0`

`<=>(x_1x_2)^2-2[(x_1+x_2)^2-2x_1x_2]-5=0`

`<=>(x_1x_2)^2-2(x_1+x_2)^2+4x_1x_2-5=0`

`<=>(2m-5)^2-2.2^2+4(2m-5)-5=0`

`<=>4m^2-20m+25-8+8m-20-5=0`

`<=>4m^2-12m-8=0`

`<=>m^2-3m-2=0`

`Delta=(-3)^2-4.1.(-2)=17>0`

`=>`pt có `2` no pb

`m_1=(3+\sqrt17)/2(ktm)`

`m_2=(3-\sqrt17)/2(tm)`

Vậy `m=(3-\sqrt17)/2`