Ta có:
$x_{1}+x_{2} = 2(m+1)$ => $x_{1} = 2m+2-x_{2}$
$x_{1}x_{2} = m^{2}+2$
=> $3x_{1}-x_{2} = 3(2m+2-x_{2})-x_{2} = 6m+6-4x_{2}=0$
=> $2x_{2} = 3m+3$ => $x_{2} = 1,5(m+1)$
$x_{1} = 2m+2-1,5m-1,5 = 0,5(m+1)$
=>$x_{1}x_{2} = 0,75(m+1)^{2}=m^{2}+2$
$0,75m^{2}+1,5m+0,75=m^{2}+2$
=> $0,25m^{2}-1,5m+1,25=0$
$m^{2}-6m+5=0$
$(m-5)(m-1)=0$
=>m=....................