把 y=3-mx 代入 x²+2y²=6 中,得x²+2(3-mx)²=6(1+2m²)x²-12mx+12=0Δ=144m²-48（1+2m²)=48m²-48当 m>1时,方程 (1+2m²)x²-12mx+12=0有两个不相等的实数根,因...