y(x²-5x+6)=x²-2x-1
整理
(y-1)x²+(2-5y)x+(6y+1)=0'
x是實(shí)數(shù),所以方程有解
判別式大于等于0
所以(2-5y)²-4(y-1)(6y-1)>=0
4-20y+25y²-24y²+28y-4>=0
y²+8y>=0
y(y+8)>=0
y=0
值域(-∞,-8]∪[0,+∞)