|-k-4-2k|/√(k^2+1)=3|3k+4|/√(k^2+1)=3|3k+4|=3√(k^2+1) 两边平方9k^2+24k+16=9k^2+924k=-7k=-7/24
|-k-4-2k|/√(k^2+1)=3|3k+4|/√(k^2+1)=3|3k+4|=3√(k^2+1)9k^2+24k+16=9k^2+924k=-7k=-7/24
